EP0239477A2 - Cerium IV compound and process for its preparation - Google Patents
Cerium IV compound and process for its preparation Download PDFInfo
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- EP0239477A2 EP0239477A2 EP87400600A EP87400600A EP0239477A2 EP 0239477 A2 EP0239477 A2 EP 0239477A2 EP 87400600 A EP87400600 A EP 87400600A EP 87400600 A EP87400600 A EP 87400600A EP 0239477 A2 EP0239477 A2 EP 0239477A2
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- European Patent Office
- Prior art keywords
- cerium
- compound
- equal
- liter
- solution
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 229910052684 Cerium Inorganic materials 0.000 title claims description 162
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 title claims description 106
- 238000000034 method Methods 0.000 title claims description 41
- 238000002360 preparation method Methods 0.000 title claims description 38
- 150000001875 compounds Chemical class 0.000 title claims description 33
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 47
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 52
- 239000002689 soil Substances 0.000 claims description 50
- 239000000243 solution Substances 0.000 claims description 49
- 238000006460 hydrolysis reaction Methods 0.000 claims description 47
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims description 44
- 239000000084 colloidal system Substances 0.000 claims description 35
- 230000007062 hydrolysis Effects 0.000 claims description 35
- 229910002651 NO3 Inorganic materials 0.000 claims description 31
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 31
- 238000003756 stirring Methods 0.000 claims description 27
- 239000002244 precipitate Substances 0.000 claims description 22
- 239000000203 mixture Substances 0.000 claims description 19
- 238000006243 chemical reaction Methods 0.000 claims description 16
- 239000012429 reaction media Substances 0.000 claims description 15
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 14
- 238000010992 reflux Methods 0.000 claims description 14
- 229910017604 nitric acid Inorganic materials 0.000 claims description 13
- 239000007864 aqueous solution Substances 0.000 claims description 12
- 150000000703 Cerium Chemical class 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 9
- 239000012266 salt solution Substances 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 8
- 150000003839 salts Chemical class 0.000 claims description 7
- 238000002425 crystallisation Methods 0.000 claims description 6
- 230000008025 crystallization Effects 0.000 claims description 6
- 229940044927 ceric oxide Drugs 0.000 claims description 4
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 150000001785 cerium compounds Chemical class 0.000 claims description 2
- 230000003301 hydrolyzing effect Effects 0.000 claims description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims description 2
- 229910052753 mercury Inorganic materials 0.000 claims description 2
- 238000000926 separation method Methods 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims 1
- 238000006056 electrooxidation reaction Methods 0.000 claims 1
- -1 cerium (IV) compound Chemical class 0.000 abstract description 57
- KKFPIBHAPSRIPB-UHFFFAOYSA-N cerium(3+);oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Ce+3].[Ce+3] KKFPIBHAPSRIPB-UHFFFAOYSA-N 0.000 description 34
- 230000000875 corresponding effect Effects 0.000 description 27
- 239000000047 product Substances 0.000 description 27
- 239000012153 distilled water Substances 0.000 description 22
- 239000002609 medium Substances 0.000 description 22
- 238000002296 dynamic light scattering Methods 0.000 description 16
- 239000000126 substance Substances 0.000 description 13
- 238000001914 filtration Methods 0.000 description 10
- 239000011521 glass Substances 0.000 description 10
- 238000004220 aggregation Methods 0.000 description 9
- 230000002776 aggregation Effects 0.000 description 9
- 238000010438 heat treatment Methods 0.000 description 9
- 238000004458 analytical method Methods 0.000 description 8
- 239000003153 chemical reaction reagent Substances 0.000 description 6
- 238000009826 distribution Methods 0.000 description 6
- 238000003860 storage Methods 0.000 description 6
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 5
- 230000001174 ascending effect Effects 0.000 description 5
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 description 4
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000001246 colloidal dispersion Methods 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 239000012736 aqueous medium Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- GHLITDDQOMIBFS-UHFFFAOYSA-H cerium(3+);tricarbonate Chemical compound [Ce+3].[Ce+3].[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O GHLITDDQOMIBFS-UHFFFAOYSA-H 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000010790 dilution Methods 0.000 description 2
- 239000012895 dilution Substances 0.000 description 2
- 238000010981 drying operation Methods 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000011541 reaction mixture Substances 0.000 description 2
- 239000003507 refrigerant Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 229910004664 Cerium(III) chloride Inorganic materials 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- VYLVYHXQOHJDJL-UHFFFAOYSA-K cerium trichloride Chemical compound Cl[Ce](Cl)Cl VYLVYHXQOHJDJL-UHFFFAOYSA-K 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000010908 decantation Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- UUZZMWZGAZGXSF-UHFFFAOYSA-N peroxynitric acid Chemical compound OON(=O)=O UUZZMWZGAZGXSF-UHFFFAOYSA-N 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229910009112 xH2O Inorganic materials 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/276—Nitrates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
- C01F17/224—Oxides or hydroxides of lanthanides
- C01F17/235—Cerium oxides or hydroxides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/01—Crystal-structural characteristics depicted by a TEM-image
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/60—Compounds characterised by their crystallite size
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
Definitions
- the present invention relates to a new cerium IV compound and one of these methods of obtaining.
- the invention aims to provide a cerium IV compound capable of being directly dispersible in water.
- a hydrated ceric dioxide can be prepared corresponding to the formula CeO2, xH2O in which x is a number between 0.5 and 2 and which is in the form of a gelatinous precipitate by addition of sodium hydroxide or ammonium to ceric salt solutions.
- cerium oxide hydrate (IV) can be carried out by precipitation from a cerium salt: thus for example, it is possible to dissolve cerous carbonate of high purity in a nitric or hydrochloric acid solution to obtain a neutral nitrate or cerous chloride solution which is oxidized with NH4OH / H2O2 to obtain the cerium oxide hydrate IV.
- the Applicant has found a directly dispersible cerium IV compound which is obtained by another route which does not involve treatment with the disintegrating agent before the colloidal dispersion is obtained.
- the cerium IV compound defined by the general formula (I) is directly dispersible in water, making it possible to obtain a colloidal dispersion of the cerium IV compound which will hereinafter be called "sol".
- composition can vary within the limits defined by formula (I) depending on the more or less advanced drying conditions of the hydrated cerium IV hydroxynitrate obtained according to a hydrolysis process, a process which constitutes a another object of the present invention.
- the present invention therefore relates to a process for the preparation of a compound corresponding to formula (I) which is characterized in that it consists in hydrolyzing an aqueous solution of a cerium IV salt in an acid medium, in separating the precipitate obtained and possibly heat treating it.
- the hydrolysis of an aqueous solution of a cerium IV salt is carried out.
- cerium IV which can be an aqueous solution of ceric nitrate.
- Said solution can contain cerium in the cerous state without disadvantage, but it is desirable to have a good precipitation yield that it contains at least 85% of cerium IV.
- the cerium salt solution is chosen so that it does not contain impurities which can be found in the final product. It may be advantageous to use a cerium salt solution having a degree of purity greater than 99%.
- the concentration of the cerium salt solution is not a critical factor, according to the invention. When it is expressed as cerium IV, it can vary between 0.3 and 3 moles per liter, preferably between 0.5 to 1.5 moles / liter.
- a ceric nitrate solution obtained by the action of nitric acid on a hydrated ceric oxide prepared in a conventional manner, by reaction of a solution of a cerous salt for example, cerous carbonate and an ammonia solution in the presence of an oxidizing agent, preferably hydrogen peroxide.
- ceric nitrate solution obtained according to the electrolytic oxidation process of a cerous nitrate solution and which is described in FR-A 2 570 087 ( o 84 13641) constitutes a raw material of choice.
- the hydrolysis medium consists of water, the nature of which is not critical and which is preferably distilled or permuted water.
- the acidity can be provided by adding a mineral acid.
- a mineral acid Preferably, nitric acid is chosen.
- An acid can be used which can be concentrated or diluted, for example, up to 10 ⁇ 2 N.
- ceric nitrate solution which can be slightly acidic and have a normality varying between 0.01 N and 5 N, preferably between 0.1 N and 1 N.
- the quantity of H ⁇ ions introduced for the hydrolysis reaction is such that the molar ratio [H+] / [Ce IV eq.] Is greater than or equal to 0 and less than or equal to 3.
- a molar ratio [H+] / [Ce IV eq.] Of between 0.4 and 2.5 is chosen.
- the proportion between the aqueous solution of cerium IV salt and the hydrolysis medium (essentially water) is such that the equivalent final concentration of cerium IV is between 0.1 mole / liter and 1 mole / liter, preferably between 0.2 and 0.6 mole / liter.
- the equivalent final cerium IV concentration is defined by the following equation: in which : - [This IV ] is the concentration in moles / liter of the solution of the cerium salt IV - V represents the volume of water possibly added with acid - V ⁇ represents the volume of the cerium IV solution.
- the hydrolysis of the cerium IV salt carried out under the conditions as described above is carried out between 70 ° C. and 120 ° C. and preferably at the reflux temperature of the reaction medium which is around 100 ° C.
- the solution of cerium IV salt in water can be added all at once, gradually or continuously, possibly containing acid brought to the reaction temperature or vice versa.
- the cerium IV salt solution and the hydrolysis medium are mixed and then the said mixture is kept maintained with stirring at the reaction temperature.
- the process can also be carried out continuously.
- the mixture of the cerium IV salt solution and the hydrolysis medium is simultaneously and continuously carried out and the mixture is continuously heated to the chosen reaction temperature.
- the duration of the hydrolysis reaction can vary between 2 and 8 hours and preferably between 3 and 6 hours. At the end of the operation, the formation of a precipitate is observed.
- the yield of the hydrolysis reaction depends on the equivalent final concentration of IV cerium and the [H+] / [Ce IV eq.] Molar ratio: the higher the reaction medium, the higher the dilution. molar ratio [H+] / [Ce IV eq.] is low. By way of example, it will be specified that it is between 100 and 25% for an equivalent final concentration in IV cerium equal to 0.35 mole / liter and a [H+] / [Ce IV eq.] Molar ratio ranging from 0 to 2.5.
- the second step of the process consists in separating after reaction the reaction mass which is in the form of a suspension whose temperature is most often between 90 ° C and 100 ° C. This operation is carried out before or after the reaction mass has cooled to room temperature, that is to say most often between 10 ° C. and 25 ° C.
- the precipitate is separated according to conventional solid-liquid separation techniques: filtration, decantation, spinning and centrifugation.
- a third step of the process of the invention consists in carrying out a heat treatment of the separated precipitate.
- This operation is optional since it has been found that the precipitate separated following the first hydrolysis step is directly dispersible in water and that it was possible to obtain an aqueous sol directly by suspending in water the separate precipitate without the need to dry it. Indeed, a drying step is not essential and elimination of all the free water is not required.
- the cerium IV compound defined by formula (Ia) corresponds to a compound of formula (I) in which p is equal to 0 and n is greater than or equal to 0 and less than or equal to approximately 20.
- the drying conditions can vary within wide limits. This is how the temperature can vary between 15 ° C and 100 ° C, preferably between room temperature and 50 ° C.
- the drying operation can be carried out in air or under reduced pressure, for example, between 1 and 10 mm of mercury (133.3322 Pa and 13332.2 Pa).
- X-ray diffraction analysis shows that a crystalline product exhibits a CeO Ce type crystalline phase having a size parameter varying from 5.41 ⁇ to 5.44 ⁇ and a crystallization rate of at least 40% and most often between 40 and 70%.
- the size of the crystallites is small since it is generally less than 60 ⁇ and, preferably, between 30 and 50 ⁇ .
- Another object of the present invention resides in the aqueous soils obtained from the cerium IV compound corresponding to formula (I).
- the present invention also provides a process for the preparation of an aqueous sol of cerium IV compound, a process according to which the cerium IV compound corresponding to formula (I) is suspended in water.
- Said compound can be dispersed in an aqueous medium or in a slightly acidic medium so that it leads to a soil whose pH is between 1 and 2.5.
- the preparation of said soil is carried out, with stirring.
- the cerium IV compound is essentially found in the form of a colloidal dispersion in water, but this does not exclude the presence of this IV in ionic form.
- the level of cerium IV in colloidal form is generally greater than 95% and preferably between 99 and 100%.
- the size of the colloids is defined by measuring the mean hydrodynamic diameter of the colloids determined by quasi-elastic light scattering according to the method described by Michael L. McConnell in Analytical Chemistry Vol. 53 No. 8 1007 (1981): said diameter may vary between 100 ⁇ and 1000 ⁇ .
- the distribution of colloid sizes is assessed in the following manner: the size of the colloids being correlated with the measurement of the translational diffusion coefficient of the particles, we highlight the uniformity of the distribution by measurement of the variance which is defined by report in which D T represents the translation scattering coefficient, an experimental quantity accessible by the quasi-elastic scattering of light. It can be seen that the variance is generally between 0.1 and 0.4 and often close to 0.2.
- the invention which consists in mixing the solution of cerium IV salt and the hydrolysis medium and in bringing said mixture to reaction temperature, according to the invention it is possible to control the size of the colloids present in the soil by varying the concentration of cerium IV and the ratio [H+] / [Ce IV eq.] defined in the hydrolysis medium.
- the size of the colloids obtained is all the smaller the higher the concentration of IV cerium and the ratio [H+] / [Ce IV eq.].
- Colloids are formed by the aggregation of elementary crystallites whose size determined by X-ray diffraction is less than 60 ⁇ and preferably between 30 and 50 ⁇ .
- the state of aggregation of the crystallites increases when the concentration of cerium IV and the ratio [H ⁇ ] / [Ce IV eq.] Increase.
- the precipitate obtained in this first hydrolysis step is then separated and then optionally subjected to a heat treatment.
- FIG. 2 illustrates the state of aggregation of a soil prepared under the same conditions except with regard to the concentration of IV cerium which is 0.46 mole / liter.
- Another embodiment of soils the colloids of which consist of a compact arrangement of elementary crystallites, consists in adding in a single step, gradually or continuously, the solution of IV cerium salt in water, possibly containing acid, carried at reaction temperature or vice versa.
- Another variant of execution is to conduct the process continuously. To this end, the mixture of the cerium IV salt solution and the hydrolysis medium is simultaneously and continuously carried out and the mixture is continuously heated to the chosen reaction temperature.
- the molar ratio [H+] / [Ce IV éq.] Is greater than or equal to 0 and less than or equal to 3 and chosen, preferably between 0 and 2.
- the soils obtained according to the invention have stability properties during storage: there is no settling after several months of storage.
- cerium IV compounds of the invention as well as the corresponding soles are synthesis intermediates for the preparation in particular of ceric oxides with a large specific surface.
- the concentration of IV cerium expressed as CeO2 is equal to 40 g / liter and the molar ratio [H+] / [Ce IV eq.] Is equal to 0.4.
- the reaction medium is kept under stirring and at reflux for 4 hours.
- the product obtained is dried in an oven at 40 ° C for 48 hours.
- the product of the invention is a crystallized product which has a CeO2 type crystalline phase. It is a fluorite-like structure, that is to say cubic face centered. A mesh parameter of 5.42 ⁇ and a crystallization rate of around 55% are determined.
- a sol is obtained having a cerium IV concentration expressed in CeO2 of 172 g / liter (1 M) and a pH close to 1.
- the soil obtained has good storage stability and does not exhibit settling for a period of at least 6 months.
- the state of aggregation of the crystallites is similar to that shown in FIG. 1.
- Example 1 is reproduced with the difference that it is implemented: - 1220 cm3 of a 0.315 N nitric acid solution - 279 cc of a ceric nitrate solution containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0.5 N.
- the concentration of IV cerium expressed as CeO2 is equal to 40 g / liter and the molar ratio [H+] / [Ce IV eq.] Is equal to 1.5.
- the reaction medium is kept under stirring and at reflux for 4 hours.
- Example 1 The product obtained is filtered and dried as in Example 1.
- a hydrolysis yield of 98.1% is determined.
- X-ray diffraction analysis makes it possible to determine a crystallization rate of the order of 65%.
- Example 1 is reproduced with the difference that it is implemented: - 1220 cm3 of a 0.6 N nitric acid solution - 279 cc of a ceric nitrate solution containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0.5 N.
- the concentration of IV cerium expressed as CeO2 is equal to 40 g / liter and the molar ratio [H ⁇ ] / [Ce IV eq.] Is equal to 2.5.
- the reaction medium is kept under stirring and at reflux for 4 hours.
- Example 1 The product obtained is filtered and dried as in Example 1.
- a hydrolysis yield of 95% is determined.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 172 g / liter.
- the soil obtained has good storage stability and does not exhibit settling for a period of at least 6 months.
- the concentration of IV cerium expressed as CeO2 is equal to 80 g / liter and the molar ratio [H+] / [Ce IV eq.] Is equal to 0.4.
- the reaction medium is kept under stirring and at reflux for 4 hours.
- Example 1 The product obtained is filtered and dried as in Example 1.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 172 g / liter (1 M) and a pH of approximately 1.2.
- the state of aggregation of the crystallites is comparable to that shown in FIG. 2.
- Example 1 is reproduced with the difference that it is implemented: - 1081 cm3 of a 0.53 N nitric acid solution - 418 cm3 of a ceric nitrate solution containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0.5 N.
- the concentration of IV cerium expressed as CeO2 is equal to 60 g / liter and the molar ratio [H+] / [Ce IV eq.] Is equal to 1.5.
- the reaction medium is kept under stirring and under reflux for 4 hours.
- Example 1 The product obtained is filtered and dried as in Example 1.
- a sol is obtained having a cerium IV concentration expressed in CeO2 of 172 g / liter (1 M) and a pH close to 1.
- the soil obtained has good storage stability and does not exhibit settling for a period of at least 6 months.
- 1.89 is introduced at room temperature into a reactor fitted with a thermometer, a stirring device, a system for introducing reagents, an ascending cooler and also equipped with a heating device. liters of distilled water.
- This solution is raised to 100 ° C., with stirring, and 1.11 liters of an ceric nitrate solution containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0.52 N.
- the concentration of IV cerium expressed as CeO2 is equal to 80 g / liter and the molar ratio [H+] / [Ce IV eq.] Is equal to 0.4.
- the reaction medium is kept under stirring and at reflux for 3 hours.
- the product obtained is dried in an oven at 40 ° C for 48 hours.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 172 g / liter (1 M).
- the concentration of IV cerium expressed as CeO2 is equal to 60 g / liter and the molar ratio [H+] / [Ce IV eq.] Is equal to 1.5.
- the reaction medium is kept under stirring and at reflux for 3 hours.
- the product obtained is dried in an oven at 40 ° C for 48 hours.
- a hydrolysis reaction yield of 82.5% is determined.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 172 g / liter (1 M).
- This solution is raised to 100 ° C., with stirring, and 545 cm3 of a ceric nitrate solution containing 1.28 moles / liter of IV cerium, 0.06 mole / liter of cerium III and having a free acidity of 0.53 N.
- the concentration of cerium IV expressed in CeO2 is equal to 40 g / liter and the molar ratio [H+] / [Ce IV eq.] Is equal to 2.5.
- the reaction medium is kept under stirring and at reflux for 3 hours.
- the product obtained is dried in an oven at 40 ° C for 48 hours.
- a hydrolysis reaction yield of 92.5% is determined.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 172 g / liter (1 M).
- a solution of distilled water is introduced simultaneously and continuously, at the rate of 430 cm3 / hour and an aqueous solution of ceric nitrate containing 1.23 moles / liter of cerium IV, 0.07 mole / liter of cerium III and having a free acidity of 0.49 N, at a rate of 170 cm3 / hour.
- a second reactor similar to the previous one is arranged so as to collect by gravity the reaction mixture coming from the first reactor.
- the product obtained is dried in an oven at 40 ° C for 48 hours.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 172 g / liter (1 M).
- an aqueous solution of 0.53 N nitric acid is added simultaneously and continuously at a rate of 430 cm3 / hour and an aqueous solution of ceric nitrate containing 1.23 moles / liter of cerium IV, 0.07 mole / liter of cerium III and having a free acidity of 0.49 N, at a rate of 170 cm3 / hour.
- the concentration of IV cerium expressed as CeO2 is equal to 60 g / liter and the molar ratio [H+] / [Ce IV eq.] Is equal to 1.5.
- the reaction mixture flows by gravity into a second reactor.
- the product obtained is dried in an oven at 40 ° C for 48 hours.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 172 g / liter (1 M).
- nitric acid 670 g of hydrated ceric oxide containing 495 g of CeO2 are introduced into hot nitric acid.
- the latter is obtained conventionally by precipitation with ammonia and hydrogen peroxide from a cerous nitrate solution (cf. FR-A-2 416 867) and is not dispersible in water.
- the concentration of IV cerium expressed as CeO2 is equal to 40 g / liter and the molar ratio [H+] / [Ce IV eq.] Is equal to 2.
- the reaction medium is kept under stirring and at reflux for 3 hours.
- a soil is obtained having a concentration of IV cerium of 1 mole / liter.
- a cerium IV compound is prepared according to the procedure of Example 4 with the exception of the drying operation which is omitted.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 172 g / liter (1 M) and a pH of approximately 1.2.
- the temperature is introduced into a 2-liter three-necked flask provided with a thermometer, a stirring device, a system for introducing reagents, an ascending refrigerant and also equipped with a heating device.
- ambient - 1425 cm3 of distilled water - 558 cm3 of a ceric nitrate solution containing 1.24 moles / liter of cerium IV, 0.06 moles / liter of cerium III and having a free acidity of 0.8 N.
- the concentration of cerium IV expressed as CeO2 is equal to 60 g / liter and the molar ratio H+ / Ce IV is equal to 0.64.
- the reaction medium is kept under stirring and at reflux for 4 hours.
- Filtration is carried out on sintered glass (porosity No. 3) thin layer ( ⁇ 5 mm) and reduced pressure (160 mm Hg) and the cup is maximally cake to ensure a high spin.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 200 g / liter (1.16 M) and a pH of 1.2.
- Example 13 is repeated, with the difference that 558 cm3 of said ceric nitrate solution in 1425 cm3 of water are introduced over 3 hours, the temperature of which has been previously brought to 100 ° C.
- the concentration of cerium IV expressed as CeO2 is equal to 60 g / liter and the molar ratio H+ / Ce IV is equal to 0.64.
- the reaction medium is kept under stirring and at reflux for 3 hours.
- Filtration is carried out on sintered glass (porosity No. 3) thin layer ( ⁇ 5 mm) and reduced pressure (160 mm Hg) and the cup is maximally cake to ensure a high spin.
- the product obtained is dried at 20 ° C for 15 h.
- a sol is obtained having a concentration of cerium IV expressed in CeO2 of 172 g / liter.
- the state of aggregation of the crystallites is high and similar to that shown in FIG. 2.
- the soil obtained has good storage stability and does not exhibit settling for a period of at least 6 months.
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Abstract
Description
La présente invention concerne un nouveau composé de cérium IV et l'un de ces procédés d'obtention.The present invention relates to a new cerium IV compound and one of these methods of obtaining.
Plus précisément, l'invention a pour but de fournir un composé de cérium IV susceptible d'être directement dispersable dans l'eau.More specifically, the invention aims to provide a cerium IV compound capable of being directly dispersible in water.
Il est connu selon l'Encyclopédie KIRK-OTHMER - Encyclopedia of Chemical Technology (deuxième édition) volume 4, p. 850 que l'on peut préparer un dioxyde cérique hydraté répondant à la formule CeO₂,xH₂O dans laquelle x est un nombre compris entre 0,5 et 2 et se présentant sous la forme d'un précipité gélatineux par addition d'hydroxyde de sodium ou d'ammonium aux solutions de sels cériques.It is known according to the KIRK-OTHMER Encyclopedia - Encyclopedia of Chemical Technology (second edition) volume 4, p. 850 that a hydrated ceric dioxide can be prepared corresponding to the formula CeO₂, xH₂O in which x is a number between 0.5 and 2 and which is in the form of a gelatinous precipitate by addition of sodium hydroxide or ammonium to ceric salt solutions.
On a proposé selon le brevet français 2 482 075 de préparer un composé de cérium IV dispersable dans l'eau selon un procédé qui consiste à disperser en milieu aqueux, un hydrate d'oxyde de cérium IV sensiblement sec ayant subi un traitement thermique entre 200°C et 450°C en présence d'un agent de désagrégation, notamment l'acide nitrique. Ainsi le chauffage en présence d'un agent de désagrégation réalise la désintégration des cristallites agrégés dans l'hydrate d'oxyde de cérium IV et produit ainsi un composé de cérium dispersable.It has been proposed according to French patent 2,482,075 to prepare a cerium IV compound dispersible in water according to a process which consists in dispersing in an aqueous medium, a substantially dry cerium IV hydrate having undergone heat treatment between 200 ° C and 450 ° C in the presence of a disintegrating agent, in particular nitric acid. Thus heating in the presence of a disintegrating agent achieves the disintegration of the aggregated crystallites in the cerium oxide hydrate IV and thus produces a dispersible cerium compound.
Il est mentionné dans ce brevet que la préparation de l'hydrate d'oxyde de cérium (IV) peut se réaliser par précipitation à partir d'un sel de cérium : ainsi par exemple, on peut dissoudre du carbonate céreux de grande pureté dans une solution d'acide nitrique ou chlorhydrique pour obtenir une solution neutre de nitrate ou chlorure céreux que l'on oxyde avec NH₄OH/H₂O₂ pour obtenir l'hydrate d'oxyde de cérium IV.It is mentioned in this patent that the preparation of the cerium oxide hydrate (IV) can be carried out by precipitation from a cerium salt: thus for example, it is possible to dissolve cerous carbonate of high purity in a nitric or hydrochloric acid solution to obtain a neutral nitrate or cerous chloride solution which is oxidized with NH₄OH / H₂O₂ to obtain the cerium oxide hydrate IV.
La demanderesse a trouvé un composé du cérium IV directement dispersable et qui est obtenu selon une autre voie ne faisant pas intervenir le traitement à l'aide de l'agent de désagrégation avant l'obtention de la dispersion colloïdale.The Applicant has found a directly dispersible cerium IV compound which is obtained by another route which does not involve treatment with the disintegrating agent before the colloidal dispersion is obtained.
Le composé de cérium IV selon l'invention répond à la formule générale (I) :
Ce(OH)x(NO₃)y, pCeO₂, nH₂O (I)
dans laquelle :
- x est tel que x = 4 - y
- y est compris entre 0,35 et 1,5
- p est supérieur ou égal à 0 et inférieur ou égal à 2,0
- n est supérieur ou égal à 0 et inférieur ou égal à environ 20The cerium IV compound according to the invention corresponds to the general formula (I):
Ce (OH) x (NO₃) y , pCeO₂, nH₂O (I)
in which :
- x is such that x = 4 - y
- is between 0.35 and 1.5
- p is greater than or equal to 0 and less than or equal to 2.0
- n is greater than or equal to 0 and less than or equal to about 20
Le composé de cérium IV défini par la formule générale (I) est directement dispersable dans l'eau permettant d'obtenir une dispersion colloïdale du composé de cérium IV que l'on dénommera par la suite sous le nom de "sol".The cerium IV compound defined by the general formula (I) is directly dispersible in water, making it possible to obtain a colloidal dispersion of the cerium IV compound which will hereinafter be called "sol".
Sa composition, précisée ci-après, peut varier dans les limites définies par la formule (I) en fonction des conditions de séchage plus ou moins poussée de l'hydroxynitrate de cérium IV hydratée obtenue selon un procédé d'hydrolyse, procédé qui constitue un autre objet de la présente invention.Its composition, specified below, can vary within the limits defined by formula (I) depending on the more or less advanced drying conditions of the hydrated cerium IV hydroxynitrate obtained according to a hydrolysis process, a process which constitutes a another object of the present invention.
La présente invention concerne donc un procédé de préparation d'un composé répondant à la formule (I) qui est caractérisé par le fait qu'il consiste à hydrolyser une solution aqueuse d'un sel de cérium IV en milieu acide, à séparer le précipité obtenu et à le traiter éventuellement thermiquement.The present invention therefore relates to a process for the preparation of a compound corresponding to formula (I) which is characterized in that it consists in hydrolyzing an aqueous solution of a cerium IV salt in an acid medium, in separating the precipitate obtained and possibly heat treating it.
Dans la première étape, on réalise l'hydrolyse d'une solution aqueuse d'un sel de cérium IV.In the first step, the hydrolysis of an aqueous solution of a cerium IV salt is carried out.
A cet effet, on part d'une solution de cérium IV qui peut être une solution aqueuse de nitrate cérique. Ladite solution peut contenir sans inconvénient du cérium à l'état céreux mais il est souhaitable pour avoir un bon rendement de précipitation qu'elle contienne au moins 85 % de cérium IV.For this purpose, one starts with a solution of cerium IV which can be an aqueous solution of ceric nitrate. Said solution can contain cerium in the cerous state without disadvantage, but it is desirable to have a good precipitation yield that it contains at least 85% of cerium IV.
La solution de sel de cérium est choisie de telle sorte qu'elle ne contienne pas d'impuretés qui puissent se retrouver, dans le produit final. Il peut être avantageux de mettre en jeu une solution de sel de cérium présentant un degré de pureté supérieure à 99 %.The cerium salt solution is chosen so that it does not contain impurities which can be found in the final product. It may be advantageous to use a cerium salt solution having a degree of purity greater than 99%.
La concentration de la solution de sel de cérium n'est pas un facteur critique, selon l'invention. Lorsqu'elle est exprimée en cérium IV, elle peut varier entre 0,3 et 3 moles par litre de préférence entre 0,5 à 1,5 moles/litre.The concentration of the cerium salt solution is not a critical factor, according to the invention. When it is expressed as cerium IV, it can vary between 0.3 and 3 moles per liter, preferably between 0.5 to 1.5 moles / liter.
A titre de matières premières, on peut faire appel à une solution de nitrate cérique obtenue par action de l'acide nitrique sur un oxyde cérique hydraté préparé d'une manière classique, par réaction d'une solution d'un sel céreux par exemple, le carbonate céreux et d'une solution d'ammoniaque en présence d'un agent oxydant, de préférence, l'eau oxygénée.As raw materials, use may be made of a ceric nitrate solution obtained by the action of nitric acid on a hydrated ceric oxide prepared in a conventional manner, by reaction of a solution of a cerous salt for example, cerous carbonate and an ammonia solution in the presence of an oxidizing agent, preferably hydrogen peroxide.
La solution de nitrate cérique obtenue selon le procédé d'oxydation électrolytique d'une solution de nitrate céreux et qui est décrite dans FR-A 2 570 087 (o 84 13641) constitute une matière première de choix.The ceric nitrate solution obtained according to the electrolytic oxidation process of a cerous nitrate solution and which is described in FR-A 2 570 087 ( o 84 13641) constitutes a raw material of choice.
Le milieu d'hydrolyse est constitué par de l'eau dont la nature n'est pas critique et qui est, de préférence, de l'eau distillée ou permutée.The hydrolysis medium consists of water, the nature of which is not critical and which is preferably distilled or permuted water.
L'acidité peut être apportée par ajout d'un acide minéral. D'une manière préférentielle, on choisit l'acide nitrique. On peut utiliser un acide qui peut être concentré ou dilué, par exemple, jusqu'à 10⁻² N.The acidity can be provided by adding a mineral acid. Preferably, nitric acid is chosen. An acid can be used which can be concentrated or diluted, for example, up to 10⁻² N.
Elle peut également provenir de la solution de nitrate cérique qui peut être légèrement acide et avoir une normalité variant entre 0,01 N et 5 N de préférence entre 0,1 N et 1 N.It can also come from the ceric nitrate solution which can be slightly acidic and have a normality varying between 0.01 N and 5 N, preferably between 0.1 N and 1 N.
La quantité d'ions Hʹ introduite pour la réaction d'hydrolyse est telle que le rapport molaire[H⁺]/[CeIV éq.] est supérieur ou égal à 0 et inférieur ou égal à 3.The quantity of Hʹ ions introduced for the hydrolysis reaction is such that the molar ratio [H⁺] / [Ce IV eq.] Is greater than or equal to 0 and less than or equal to 3.
On choisit, de préférence, un rapport molaire [H⁺]/[CeIV éq.] compris entre 0,4 et 2,5.Preferably, a molar ratio [H⁺] / [Ce IV eq.] Of between 0.4 and 2.5 is chosen.
La proportion entre la solution aqueuse de sel de cérium IV et le milieu d'hydrolyse (essentiellement l'eau) est telle que la concentration finale équivalente en cérium IV est comprise entre 0.1 mole/litre et 1 mole/litre, de préférence, entre 0,2 et 0,6 mole/litre.The proportion between the aqueous solution of cerium IV salt and the hydrolysis medium (essentially water) is such that the equivalent final concentration of cerium IV is between 0.1 mole / liter and 1 mole / liter, preferably between 0.2 and 0.6 mole / liter.
On définit la concentration finale équivalente en cérium IV par l'équation suivante:
- [CeIV] est la concentration en moles/litre de la solution du sel de cérium IV
- V représente le volume d'eau éventuellement additionné d'acide
- Vʹ représente le volume de la solution de cérium IV.The equivalent final cerium IV concentration is defined by the following equation:
- [This IV ] is the concentration in moles / liter of the solution of the cerium salt IV
- V represents the volume of water possibly added with acid
- Vʹ represents the volume of the cerium IV solution.
L'hydrolyse du sel de cérium IV réalisée dans les conditions telles que décrites précédemment est effectuée entre 70°C et 120°C et de préférence à la température de reflux du milieu réactionnel qui se situe vers 100°C.The hydrolysis of the cerium IV salt carried out under the conditions as described above is carried out between 70 ° C. and 120 ° C. and preferably at the reflux temperature of the reaction medium which is around 100 ° C.
Il est plus aisé de travailler à la température de reflux qui est facile à contrôler et à reproduire.It is easier to work at the reflux temperature which is easy to control and reproduce.
On peut mettre en oeuvre le procédé de l'invention selon plusieurs variantes. Par exemple on peut additionner en une seule fois, graduellement ou en continu la solution de sel de cérium IV dans l'eau contenant éventuellement de l'acide portée à la température réactionnelle ou inversement.The method of the invention can be implemented according to several variants. For example, the solution of cerium IV salt in water can be added all at once, gradually or continuously, possibly containing acid brought to the reaction temperature or vice versa.
Selon un mode de réalisation préféré de l'invention, on mélange la solution de sel de cérium IV et le milieu d'hydrolyse puis l'on porte ledit mélange maintenu sous agitation à la température réactionnelle.According to a preferred embodiment of the invention, the cerium IV salt solution and the hydrolysis medium are mixed and then the said mixture is kept maintained with stirring at the reaction temperature.
On peut également conduire le procédé en continu. A cet effet, on effectue simultanément et en continu le mélange de la solution de sel de cérium IV et du milieu d'hydrolyse et l'on chauffe en continu le mélange, à la température réactionnelle choisie.The process can also be carried out continuously. To this end, the mixture of the cerium IV salt solution and the hydrolysis medium is simultaneously and continuously carried out and the mixture is continuously heated to the chosen reaction temperature.
La durée de la réaction d'hydrolyse peut varier entre 2 et 8 heures et de préférence, entre 3 et 6 heures. En fin d'opération, on observe la formation d'un précipité.The duration of the hydrolysis reaction can vary between 2 and 8 hours and preferably between 3 and 6 hours. At the end of the operation, the formation of a precipitate is observed.
Le rendement de la réaction d'hydrolyse dépend de la concentration finale équivalente en cérium IV et du rapport molaire [H⁺]/[CeIV éq.] : il est d'autant plus élevé que le milieu réactionnel est plus dilué et que le rapport molaire [H⁺]/[CeIV éq.] est faible. A titre d'exemples on précisera qu'il se situe entre 100 et 25 % pour une concentration finale équivalente en cérium IV égale à 0,35 mole/litre et un rapport molaire [H⁺]/[CeIV éq.] allant de 0 à 2,5.The yield of the hydrolysis reaction depends on the equivalent final concentration of IV cerium and the [H⁺] / [Ce IV eq.] Molar ratio: the higher the reaction medium, the higher the dilution. molar ratio [H⁺] / [Ce IV eq.] is low. By way of example, it will be specified that it is between 100 and 25% for an equivalent final concentration in IV cerium equal to 0.35 mole / liter and a [H⁺] / [Ce IV eq.] Molar ratio ranging from 0 to 2.5.
La deuxième étape du procédé consiste à séparer après réaction la masse réactionnelle qui se présente sous la forme d'une suspension dont la température se situe le plus souvent entre 90°C et 100°C. Cette opération est effectuée avant ou après refroidissement de la masse réactionnelle à température ambiante c'est-à-dire le plus souvent entre 10°C et 25°C.The second step of the process consists in separating after reaction the reaction mass which is in the form of a suspension whose temperature is most often between 90 ° C and 100 ° C. This operation is carried out before or after the reaction mass has cooled to room temperature, that is to say most often between 10 ° C. and 25 ° C.
On sépare le précipité selon les techniques classiques de séparation solide-liquide : filtration, décantation, essorage et centrifugation.The precipitate is separated according to conventional solid-liquid separation techniques: filtration, decantation, spinning and centrifugation.
Une troisième étape du procédé de l'invention consiste à effectuer un traitement thermique du précipité séparé.A third step of the process of the invention consists in carrying out a heat treatment of the separated precipitate.
Cette opération est facultative car il a été trouvé que le précipité séparé suite à la première étape d'hydrolyse était directement dispersable dans l'eau et qu'il était possible d'obtenir directement un sol aqueux par mise en suspension dans l'eau du précipité séparé sans qu'il soit nécessaire de le sécher. En effet, une étape de séchage n'est pas indispensable et une élimination de toute l'eau libre n'est pas requise.This operation is optional since it has been found that the precipitate separated following the first hydrolysis step is directly dispersible in water and that it was possible to obtain an aqueous sol directly by suspending in water the separate precipitate without the need to dry it. Indeed, a drying step is not essential and elimination of all the free water is not required.
Dans ce cas, le produit obtenu répond à la formule (Ia) :
Ce(OH)x(NO₃)y,nH₂O (Ia)
dans laquelle :
- x est tel que x = 4 - y
- y est compris entre 0,35 et 0,7
- n est supérieur ou égal à 0 et inférieur ou égal à environ 20In this case, the product obtained corresponds to formula (Ia):
Ce (OH) x (NO₃) y , nH₂O (Ia)
in which :
- x is such that x = 4 - y
- is between 0.35 and 0.7
- n is greater than or equal to 0 and less than or equal to about 20
Le composé du cérium IV défini par la formule (Ia) correspond à un composé de formule (I) dans laquelle p est égal à 0 et n est supérieur ou égal à 0 et inférieur ou égal à environ 20.The cerium IV compound defined by formula (Ia) corresponds to a compound of formula (I) in which p is equal to 0 and n is greater than or equal to 0 and less than or equal to approximately 20.
En soumettant le précipité séparé à une étape de séchage en contrôlant les paramètres durée et température, on obtient selon un accroissement de ses paramètres, un composé de cérium IV répondant à la formula (Ia) dans laquelle n est supérieur ou égal à 0 et inférieur ou égal à environ 20, un composé de cérium IV répondant à la formule (Ib) correspondant à un composé de formule (I) dans laquelle n et p sont égaux à 0, un composé de cérium IV répondant à la formule (Ic) correspondant à un composé de formule (I) dans laquelle n est égal à 0 et p est supérieur à 0.By subjecting the separated precipitate to a drying step while controlling the duration and temperature parameters, an increase in its parameters is obtained, a cerium IV compound corresponding to the formula (Ia) in which n is greater than or equal to 0 and less or equal to about 20, a cerium IV compound corresponding to formula (Ib) corresponding to a compound of formula (I) in which n and p are equal to 0, a cerium IV compound corresponding to formula (Ic) to a compound of formula (I) in which n is equal to 0 and p is greater than 0.
Plus précisément, le composé de cérium IV est représenté par la formule (Ib) qui est la suivante :
Ce(OH)x(NO₃)y (Ib)
dans ladite formule :
- x est tel que x = 4 - y
- y est compris entre 0,35 et 0,7
- la teneur en cérium exprimée en % de CeO₂ est comprise entre 77 et 72 %.More specifically, the cerium IV compound is represented by the formula (Ib) which is as follows:
Ce (OH) x (NO₃) y (Ib)
in said formula:
- x is such that x = 4 - y
- is between 0.35 and 0.7
- the cerium content expressed in% of CeO₂ is between 77 and 72%.
Si les conditions de séchage sont plus poussées et que la teneur en CeO₂ dépasse 72 % pour y = 0,7, 77 % pour y = 0,35 et une valeur comprise entre 77 et 72 % pour y compris entre 0,35 et 0,7 on peut représenter le composé obtenu par la formule suivante (Ic) qui met en évidence la présence d'oxyde cérique :
Ce(OH)x(NO₃)y,pCeO₂ (Ic)
dans ladite formule :
- x est tel que x = 4 - y
- y est compris entre 0,35 et 1,5
- p est supérieur à 0 et inférieur ou égal à 2,0If the drying conditions are more advanced and the CeO₂ content exceeds 72% for y = 0.7, 77% for y = 0.35 and a value between 77 and 72% for including between 0.35 and 0 , 7 the compound obtained can be represented by the following formula (Ic) which highlights the presence of ceric oxide:
Ce (OH) x (NO₃) y , pCeO₂ (Ic)
in said formula:
- x is such that x = 4 - y
- is between 0.35 and 1.5
- p is greater than 0 and less than or equal to 2.0
Les conditions de séchage peuvent varier dans de larges limites. C'est ainsi que la température peut varier entre 15°C et 100°C de préférence entre la température ambiante et 50°C. La durée de séchage est choisie de préférence entre 5 et 48 heures afin d'obtenir un produit sec (n = 0). L'opération de séchage peut être faite à l'air ou sous pression réduite, par exemple, entre 1 et 10 mm de mercure (133,3322 Pa et 13332,2 Pa).The drying conditions can vary within wide limits. This is how the temperature can vary between 15 ° C and 100 ° C, preferably between room temperature and 50 ° C. The drying time is preferably chosen between 5 and 48 hours in order to obtain a dry product (n = 0). The drying operation can be carried out in air or under reduced pressure, for example, between 1 and 10 mm of mercury (133.3322 Pa and 13332.2 Pa).
Dans le cas où l'on obtient un produit sec, c'est-à-dire que le composé obtenu répond à la formule (I) dans laquelle n est égal à 0, on note l'obtention d'un produit cristallisé.In the case where a dry product is obtained, that is to say that the compound obtained corresponds to formula (I) in which n is equal to 0, it is noted that a crystallized product is obtained.
L'analyse par diffraction X montre que c'est un produit cristallisé que présente une phase cristalline de type CeO₂ ayant un paramètre de taille variant de 5,41 Å à 5,44 Å et un taux de cristallisation d'au moins 40 % et le plus souvent compris entre 40 et 70 %. Dans la partie cristallisée, la taille des cristallites est faible puisqu'elle est généralement inférieure à 60 Å et, de préférence, comprise entre 30 et 50 Å.X-ray diffraction analysis shows that a crystalline product exhibits a CeO Ce type crystalline phase having a size parameter varying from 5.41 Å to 5.44 Å and a crystallization rate of at least 40% and most often between 40 and 70%. In the crystallized part, the size of the crystallites is small since it is generally less than 60 Å and, preferably, between 30 and 50 Å.
Qu'il réponde à la formule (Ia), (Ib) ou (Ic), le composé de l'invention représenté globalement par la formule (I) est directement dispersable dans l'eau.Whether it corresponds to formula (Ia), (Ib) or (Ic), the compound of the invention generally represented by formula (I) is directly dispersible in water.
Un autre objet de la présente invention réside dans les sols aqueux obtenus à partir du composé de cérium IV répondant à la formule (I).Another object of the present invention resides in the aqueous soils obtained from the cerium IV compound corresponding to formula (I).
La présente invention propose également un procédé de préparation d'un sol aqueux de composé de cérium IV, procédé selon lequel on met en suspension dans l'eau, le composé de cérium IV répondant à la formule (I).The present invention also provides a process for the preparation of an aqueous sol of cerium IV compound, a process according to which the cerium IV compound corresponding to formula (I) is suspended in water.
Ledit composé peut être dispersé en milieu aqueux ou en milieu légèrement acide de telle sorte qu'il conduit à un sol dont le pH est compris entre 1 et 2,5.Said compound can be dispersed in an aqueous medium or in a slightly acidic medium so that it leads to a soil whose pH is between 1 and 2.5.
Pour ce qui est de l'eau, sa nature n'est pas critique et sa température est généralement la température ambiante.As for water, its nature is not critical and its temperature is generally room temperature.
D'une manière préférentielle, on effectue la préparation dudit sol, sous agitation.Preferably, the preparation of said soil is carried out, with stirring.
Dans les sols obtenus selon l'invention, le composé de cérium IV se trouve essentiellement sous la forme d'une dispersion colloïdale dans l'eau mais ceci n'exclut pas la présence de Ce IV sous forme ionique.In the soils obtained according to the invention, the cerium IV compound is essentially found in the form of a colloidal dispersion in water, but this does not exclude the presence of this IV in ionic form.
Le taux de cérium IV sous forme colloïdale est généralement supérieur à 95 % et de préférence compris entre 99 et 100 %.The level of cerium IV in colloidal form is generally greater than 95% and preferably between 99 and 100%.
On peut préparer selon l'invention un sol aqueux de composé de cérium IV dont la concentration exprimée en CeO₂ peut atteindre jusqu'à 2 moles par litre et est comprise de préférence entre 0,5 et 1,0 mole/litre.One can prepare according to the invention an aqueous sol of cerium IV compound whose concentration expressed as CeO₂ can reach up to 2 moles per liter and is preferably between 0.5 and 1.0 mole / liter.
On peut obtenir un sol dont la taille des colloïdes peut varier dans une gamme assez large.One can obtain a soil the size of the colloids of which can vary within a fairly wide range.
La taille des colloïdes est définie par la mesure du diamètre hydrodynamique moyen des colloïdes déterminé par diffusion quasi-élastique de la lumière selon la méthode décrite par Michael L. McConnell dans Analytical Chemistry Vol. 53 no 8 1007 A (1981) : ledit diamètre peut varier entre 100 Å et 1000Å.The size of the colloids is defined by measuring the mean hydrodynamic diameter of the colloids determined by quasi-elastic light scattering according to the method described by Michael L. McConnell in Analytical Chemistry Vol. 53 No. 8 1007 (1981): said diameter may vary between 100Å and 1000Å.
La distribution des tailles de colloïdes est appréciée de la manière qui suit : la taille des colloïdes étant corrélée avec la mesure du coefficient de diffusion de translation des particules, on met en évidence le caractère uniforme de la distribution par mesure de la variance qui est définie par le rapport
Suivant le mode préféré de réalisation de l'invention qui consiste à mélanger la solution de sel de cérium IV et le milieu d'hydrolyse et à porter ledit mélange à la température réactionelle, on parvient selon l'invention à contrôler la taille des colloïdes présents dans le sol en faisant varier la concentration du cérium IV et le rapport [H⁺]/[CeIV éq.] définis dans le milieu d'hydrolyse.According to the preferred embodiment of the invention which consists in mixing the solution of cerium IV salt and the hydrolysis medium and in bringing said mixture to reaction temperature, according to the invention it is possible to control the size of the colloids present in the soil by varying the concentration of cerium IV and the ratio [H⁺] / [Ce IV eq.] defined in the hydrolysis medium.
La taille des colloïdes obtenus est d'autant plus petite que la concentration en cérium IV et le rapport [H⁺]/[CeIV éq.] sont d'autant plus grands.The size of the colloids obtained is all the smaller the higher the concentration of IV cerium and the ratio [H⁺] / [Ce IV eq.].
Les colloïdes sont constitués par l'agrégation de cristallites élémentaires dont la taille déterminée par diffraction X est inférieure à 60 Å et de préférence, comprise entre 30 et 50 Å.Colloids are formed by the aggregation of elementary crystallites whose size determined by X-ray diffraction is less than 60 Å and preferably between 30 and 50 Å.
On réussit selon l'invention à contrôler l'état d'agrégation des cristallites élémentaires en jouant sur la concentration du cérium IV et sur le rapport [Hʹ]/[CeIV éq.] définis dans le milieu d'hydrolyse.One succeeds according to the invention in controlling the state of aggregation of elementary crystallites by varying the concentration of cerium IV and the ratio [Hʹ] / [Ce IV eq.] Defined in the hydrolysis medium.
L'état d'agrégation des cristallites croît lorsque la concentration en cérium IV et le rapport [Hʹ]/[CeIV éq.] augmentent.The state of aggregation of the crystallites increases when the concentration of cerium IV and the ratio [Hʹ] / [Ce IV eq.] Increase.
Lorsque la concentration finale équivalente en cérium IV est inférieure à 0,4 mole/litre et que le rapport [Hʹ]/[CeIV éq.] est inférieur ou égal à 0,75, on obtient des sols dont les colloïdes sont constitués par un arrangement peu compact des cristallites élémentaires.When the final equivalent concentration of IV cerium is less than 0.4 mole / liter and the ratio [Hʹ] / [Ce IV eq.] Is less than or equal to 0.75, soils are obtained whose colloids are constituted by an uncompact arrangement of the elementary crystallites.
Lorsque la concentration finale équivalente en cérium IV est supérieure ou égale à 0,4 mole/litre et le rapport [Hʹ]/[CeIV éq.] est supérieur ou égal à 0 et inférieur à 0,75 ou quelle que soit la concentration finale équivalente en cérium IV lorsque le rapport [Hʹ]/[CeIV éq.] est supérieur à 0,75 et inférieur ou égal à 3, on obtient des sols constitués par un arrangement plus compact des cristallites élémentaires.When the final equivalent concentration in IV cerium is greater than or equal to 0.4 mol / liter and the ratio [Hʹ] / [Ce IV eq.] Is greater than or equal to 0 and less than 0.75 or whatever the concentration equivalent final in cerium IV when the ratio [Hʹ] / [Ce IV eq.] is greater than 0.75 and less than or equal to 3, soils are obtained which consist of a more compact arrangement of the elementary crystallites.
Le précipité obtenu à cette première étape d'hydrolyse est ensuite séparé puis soumis éventuellement à un traitement thermique.The precipitate obtained in this first hydrolysis step is then separated and then optionally subjected to a heat treatment.
A titre illustratif, on se référera aux figures 1 et 2 qui représentent des photographies prises au microscope électronique en transmission (G = 110 000) mettant en évidence l'état d'agrégation des cristallites.By way of illustration, reference is made to FIGS. 1 and 2 which represent photographs taken with the transmission electron microscope (G = 110,000) highlighting the state of aggregation of the crystallites.
La figure 1 correspond à l'état d'agrégation d'un sol qui est préparé à partir d'un composé de cérium IV préparé selon le mode opératoire de l'exemple 1 dans les conditions d'hydrolyse suivantes : [Ce IV] = 0,23 mole/litre et rapport [Hʹ]/[CeIV éq.] = 0,5 : ledit sol étant séché à 80°C.FIG. 1 corresponds to the state of aggregation of a sol which is prepared from a cerium IV compound prepared according to the procedure of Example 1 under the following hydrolysis conditions: [Ce IV] = 0.23 mole / liter and ratio [Hʹ] / [Ce IV eq.] = 0.5: said soil being dried at 80 ° C.
La figure 2 illustre l'état d'agrégation d'un sol préparé dans les mêmes conditions sauf en ce qui concerne la concentration en cérium IV qui est de 0,46 mole/litre.FIG. 2 illustrates the state of aggregation of a soil prepared under the same conditions except with regard to the concentration of IV cerium which is 0.46 mole / liter.
La comparaison des deux figures montre que l'arrangement des cristallites est plus lâche lorsque la concentration en cérium IV diminue.The comparison of the two figures shows that the arrangement of the crystallites is looser when the concentration of IV cerium decreases.
Un autre mode de réalisation de sols dont les colloïdes sont constitués par un arrangement compact des cristallites élémentaire consiste à additionner en une seule fois, graduellement ou en continu la solution de sel de cérium IV dans l'eau contenant éventuellement de l'acide, portée à la température réactionnelle ou inversement.Another embodiment of soils, the colloids of which consist of a compact arrangement of elementary crystallites, consists in adding in a single step, gradually or continuously, the solution of IV cerium salt in water, possibly containing acid, carried at reaction temperature or vice versa.
Une autre variante d'exécution est de conduire le procédé en continu. A cet effet, on effectue simultanément et en continu le mélange de la solution de sel de cérium IV et du milieu d'hydrolyse et l'on chauffe en continu le mélange, à la température réactionnelle choisie.Another variant of execution is to conduct the process continuously. To this end, the mixture of the cerium IV salt solution and the hydrolysis medium is simultaneously and continuously carried out and the mixture is continuously heated to the chosen reaction temperature.
Lorsque les deux solutions de départ sont mises en oeuvre selon les modes d'exécution exposés ci-dessus, le rapport molaire [H⁺]/[CeIV éq.] est supérieur ou égal à 0 et inférieur ou égal à 3 et choisi, de préférence, entre 0 et 2.When the two starting solutions are implemented according to the embodiments described above, the molar ratio [H⁺] / [Ce IV éq.] Is greater than or equal to 0 and less than or equal to 3 and chosen, preferably between 0 and 2.
Les sols obtenus selon l'invention présentent des propriétés de stabilité au cours du stockage : il n'y a pas de décantation après plusieurs mois de stockage.The soils obtained according to the invention have stability properties during storage: there is no settling after several months of storage.
Par basification jusqu'à obtention d'un pH d'environ 3,0 effectuée de préférence par addition d'une solution aqueuse d'ammoniaque, on peut également obtenir de plus gros colloïdes dont le diamètre hydrodynamique se situe alors entre 300 et 2000 Å.By basification until a pH of approximately 3.0 is obtained, preferably by addition of an aqueous ammonia solution, it is also possible to obtain larger colloids, the hydrodynamic diameter of which is then between 300 and 2000 Å. .
Les composés de cérium IV de l'invention ainsi que les sols correspondants sont des intermédiaires de synthèse pour la préparation notamment d'oxydes cériques à grande surface spécifique.The cerium IV compounds of the invention as well as the corresponding soles are synthesis intermediates for the preparation in particular of ceric oxides with a large specific surface.
On donne ci-après des exemples qui illustrent l'invention sans toutefois la limiter.Examples are given below which illustrate the invention without, however, limiting it.
Dans les exemples, les pourcentages donnés sont exprimés en poids.In the examples, the percentages given are expressed by weight.
Dans un ballon tricol de 2 litres muni d'un thermomètre, d'un dispositif d'agitation, d'un système d'introduction de réactifs, d'un réfrigérant ascendant et équipé également d'un dispositif de chauffage, on introduit à température ambiante :
- 1220 cm³ d'eau distillée
- 279 cm³ d'une solution de nitrate cérique préparée par électrolyse conformément à FR-A 2 570 087 et contenant 1,25 moles/litre de cérium IV, 0,05 mole/litre de cérium III et ayant une acidité libre de 0,5 N.In a 2-liter three-necked flask fitted with a thermometer, a stirring device, a system for introducing reagents, a ascending refrigerant and also equipped with a heating device, the following are introduced at ambient temperature:
- 1220 cm³ of distilled water
- 279 cc of a ceric nitrate solution prepared by electrolysis in accordance with FR-A 2 570 087 and containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0, 5 N.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 40 g/litre et le rapport molaire [H⁺]/[CeIV éq.] est égal à 0,4.In the hydrolysis medium, the concentration of IV cerium expressed as CeO₂ is equal to 40 g / liter and the molar ratio [H⁺] / [Ce IV eq.] Is equal to 0.4.
On maintient le milieu réactionnel sous agitation et au reflux pendant 4 heures.The reaction medium is kept under stirring and at reflux for 4 hours.
On effectue la filtration sur verre fritté (porosité no 3).Filtration is carried out on sintered glass (porosity No. 3).
On sèche le produit obtenu dans une étuve à 40°C pendant 48 heures.The product obtained is dried in an oven at 40 ° C for 48 hours.
On recueille 73,5 g d'un précipité jaune.73.5 g of a yellow precipitate are collected.
L'analyse chimique du produit obtenu montre qu'il présente la composition suivante :
- perte au feu = 20 %
- CeO₂ = 80 %
- rapport molaire NO₃⁻ /CeIV = 0,45Chemical analysis of the product obtained shows that it has the following composition:
- loss on ignition = 20%
- CeO₂ = 80%
- NO₃⁻ / Ce IV molar ratio = 0.45
On détermine un rendement de réaction d'hydrolyse de 98 %.A 98% hydrolysis reaction yield is determined.
L'analyse par diffraction X montre que le produit de l'invention est un produit cristallisé qui présente une phase cristalline de type CeO₂. C'est une structure type fluorine c'est-à-dire cubique face centrée. On détermine un paramètre de maille de 5,42 Å et un taux de cristallisation d'environ 55 %.X-ray diffraction analysis shows that the product of the invention is a crystallized product which has a CeO₂ type crystalline phase. It is a fluorite-like structure, that is to say cubic face centered. A mesh parameter of 5.42 Å and a crystallization rate of around 55% are determined.
On additionne 43 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 200 cm³.43 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 200 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre (1 M) et un pH voisin de 1.A sol is obtained having a cerium IV concentration expressed in CeO₂ of 172 g / liter (1 M) and a pH close to 1.
L'examen par diffusion quasi-élastique de la lumière montre la présence de colloïdes de diamètre hydrodynamique moyen de l'ordre de 900 Å présentant une répartition de taille de colloïdes caractérisée par sa variance égale à 0,3.Examination by quasi-elastic light scattering shows the presence of colloids of average hydrodynamic diameter of the order of 900 Å having a size distribution of colloids characterized by its variance equal to 0.3.
On remarque que le sol obtenu présente une bonne stabilité au stockage et ne présente pas de décantation pour une durée d'au moins 6 mois.It is noted that the soil obtained has good storage stability and does not exhibit settling for a period of at least 6 months.
L'état d'aggrégation des cristallites est semblable à celui mis en évidence par la figure 1.The state of aggregation of the crystallites is similar to that shown in FIG. 1.
On reproduit l'exemple 1 à la différence près que l'on met en oeuvre :
- 1220 cm³ d'une solution d'acide nitrique 0,315 N
- 279 cm³ d'une solution de nitrate cérique contenant 1,25 moles/litre de cérium IV, 0,05 mole/litre de cérium III et ayant une acidité libre de 0,5 N.Example 1 is reproduced with the difference that it is implemented:
- 1220 cm³ of a 0.315 N nitric acid solution
- 279 cc of a ceric nitrate solution containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0.5 N.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 40 g/litre et le rapport molaire [H⁺]/[CeIV éq.] est égal à 1,5.In the hydrolysis medium, the concentration of IV cerium expressed as CeO₂ is equal to 40 g / liter and the molar ratio [H⁺] / [Ce IV eq.] Is equal to 1.5.
On maintient le milieu réactionnel sous agitation et au reflux pendant 4 heures.The reaction medium is kept under stirring and at reflux for 4 hours.
On effectue la filtration et le séchage du produit obtenu comme dans l'exemple 1.The product obtained is filtered and dried as in Example 1.
On recueille 76 g d'un précipité jaune.76 g of a yellow precipitate are collected.
L'analyse chimique du produit obtenu montre qu'il présente la composition chimique suivante :
- perte au feu = 22,5 %
- CeO₂ = 77,5 %Chemical analysis of the product obtained shows that it has the following chemical composition:
- loss on ignition = 22.5%
- CeO₂ = 77.5%
On détermine un rendement d'hydrolyse de 98,1 %.A hydrolysis yield of 98.1% is determined.
L'analyse par diffraction X permet de déterminer un taux de cristallisation de l'ordre de 65 %.X-ray diffraction analysis makes it possible to determine a crystallization rate of the order of 65%.
On additionne 44,4 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suiffisante pour obtenir un volume de 200 cm³.44.4 g of the compound prepared according to a) are added to distilled water used in a sufficient amount to obtain a volume of 200 cm³.
L'examen du sol obtenu par diffusion quasi-élastique de la lumière révèle la présence de colloïdes ayant un diamètre hydrodynamique moyen d'environ 600 Å et une réparatition de taille de colloïdes caractérisé par une variance égale à 0,15.Examination of the soil obtained by quasi-elastic light scattering reveals the presence of colloids having an average hydrodynamic diameter of approximately 600 Å and a size repair of colloids characterized by a variance equal to 0.15.
On reproduit l'exemple 1 à la différence près que l'on met en oeuvre :
- 1220 cm³ d'une solution d'acide nitrique 0,6 N
- 279 cm³ d'une solution de nitrate cérique contenant 1,25 moles/litre de cérium IV, 0,05 mole/litre de cérium III et ayant une acidité libre de 0,5 N.Example 1 is reproduced with the difference that it is implemented:
- 1220 cm³ of a 0.6 N nitric acid solution
- 279 cc of a ceric nitrate solution containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0.5 N.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 40 g/litre et le rapport molaire [Hʹ]/[CeIV éq.] est égal à 2,5.In the hydrolysis medium, the concentration of IV cerium expressed as CeO₂ is equal to 40 g / liter and the molar ratio [Hʹ] / [Ce IV eq.] Is equal to 2.5.
On maintient le milieu réactionnel sous agitation et au reflux pendant 4 heures.The reaction medium is kept under stirring and at reflux for 4 hours.
On effectue la filtration et le séchage du produit obtenu comme dans l'exemple 1.The product obtained is filtered and dried as in Example 1.
On recueille 68,2 g d'un précipité jaune.68.2 g of a yellow precipitate are collected.
L'analyse chimique du produit obtenu présente la composition chimique suivante :
- perte au feu = 16,6 %
- CeO₂ = 83,4 %
- rapport molaire NO₃⁻/CeIV = 0,48The chemical analysis of the product obtained has the following chemical composition:
- loss on ignition = 16.6%
- CeO₂ = 83.4%
- NO₃⁻ / Ce IV molar ratio = 0.48
On détermine un rendement d'hydrolyse de 95 %.A hydrolysis yield of 95% is determined.
On additionne 42,75 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 200 cm³.42.75 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 200 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre.A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 172 g / liter.
L'examen du sol obtenu par diffusion quasi-élastique de la lumière révèle la présence de colloïdes ayant un diamètre hydrodynamique moyen d'environ 500 Å.Examination of the soil obtained by quasi-elastic light scattering reveals the presence of colloids having an average hydrodynamic diameter of around 500 Å.
On remarque que le sol obtenu présente une bonne stabilité au stockage et ne présente pas de décantation pour une durée d'au moins 6 mois.It is noted that the soil obtained has good storage stability and does not exhibit settling for a period of at least 6 months.
On part des réactifs suivants :
- 942 cm³ d'eau distillée
- 558 cm³ d'une solution de nitrate cérique contenant 1,25 moles/litre de cérium IV, 0,05 mole/litre de cérium III et ayant une acidité libre de 0,5 NWe start from the following reagents:
- 942 cm³ of distilled water
- 558 cm³ of a ceric nitrate solution containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0.5 N
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 80 g/litre et le rapport molaire [H⁺]/[CeIV éq.] est égal à 0,4.In the hydrolysis medium, the concentration of IV cerium expressed as CeO₂ is equal to 80 g / liter and the molar ratio [H⁺] / [Ce IV eq.] Is equal to 0.4.
On maintient le milieu réactionnel sous agitation et au reflux pendant 4 heures.The reaction medium is kept under stirring and at reflux for 4 hours.
On effectue la filtration et le séchage du produit obtenu comme dans l'exemple 1.The product obtained is filtered and dried as in Example 1.
On recueille 114 g d'un précipité jaune.114 g of a yellow precipitate are collected.
L'analyse chimique du produit obtenu montre qu'il présente la composition chimique suivante :
- perte au feu = 18 %
- CeO₂ = 82 %
- rapport molaire NO₃⁻/CeIV = 0,43Chemical analysis of the product obtained shows that it has the following chemical composition:
- loss on ignition = 18%
- CeO₂ = 82%
- NO₃⁻ / Ce IV molar ratio = 0.43
On détermine un rendement de la réaction d'hydrolyse de 78 %.A yield of the hydrolysis reaction of 78% is determined.
On additionne 41,9 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 200 cm³.41.9 g of the compound prepared according to a) are added to distilled water used in an amount sufficient to obtain a volume of 200 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre (1 M) et un pH d'environ 1,2.A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 172 g / liter (1 M) and a pH of approximately 1.2.
L'examen du sol obtenu par diffusion quasi-élastique de la lumière révèle la présence de colloïdes ayant un diamètre hydrodynamique moyen de l'ordre de 650 Å et une répartition de taille de colloïdes caractérisée par une variance égale à 0,2.Examination of the soil obtained by quasi-elastic light scattering reveals the presence of colloids having an average hydrodynamic diameter of the order of 650 Å and a size distribution of colloids characterized by a variance equal to 0.2.
L'état d'aggrégation des cristallites est comparable à celui mis en évidence par la figure 2.The state of aggregation of the crystallites is comparable to that shown in FIG. 2.
La comparaison des figures 1 et 2 montre que dans le cas présent l'arrangement des cristallites est beaucoup plus compact.The comparison of Figures 1 and 2 shows that in the present case the arrangement of the crystallites is much more compact.
Par addition progressive d'une solution d'ammoniaque 1,3 N à raison de 20 cm³/heure au sol précédemment synthétisé et dilué par de l'eau distillée jusqu'à obtention d'une concentration en cérium égale à 0,5 M, il est possible d'obtenir un sol à pH plus élevé, jusqu'à un pH de 3,0.By progressive addition of a 1.3 N ammonia solution at the rate of 20 cm³ / hour to the previously synthesized soil and diluted with distilled water until a cerium concentration equal to 0.5 M is obtained, it is possible to obtain a soil with a higher pH, up to a pH of 3.0.
L'examen du sol après dilution 1/100 par diffusion quasi-élastique de la lumière montre la présence de colloïdes de diamètre hydrodynamique moyen de l'ordre de 2000 Å.Examination of the soil after 1/100 dilution by quasi-elastic light scattering shows the presence of colloids with an average hydrodynamic diameter of around 2000 Å.
On reproduit l'exemple 1 à la différence près que l'on met en oeuvre :
- 1081 cm³ d'une solution d'acide nitrique 0,53 N
- 418 cm³ d'une solution de nitrate cérique contenant 1,25 moles/litre de cérium IV, 0,05 mole/litre de cérium III et ayant une acidité libre de 0,5 N.Example 1 is reproduced with the difference that it is implemented:
- 1081 cm³ of a 0.53 N nitric acid solution
- 418 cm³ of a ceric nitrate solution containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0.5 N.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 60 g/litre et le rapport molaire [H⁺]/[CeIV éq.] est égal à 1.5.In the hydrolysis medium, the concentration of IV cerium expressed as CeO₂ is equal to 60 g / liter and the molar ratio [H⁺] / [Ce IV eq.] Is equal to 1.5.
On maintient le milieu réactionel sous agitation et sous reflux pendant 4 heures.The reaction medium is kept under stirring and under reflux for 4 hours.
On effectue la filtration et le séchage du produit obtenu comme dans l'exemple 1.The product obtained is filtered and dried as in Example 1.
On recueille 90 g d'un précipité jaune présentant une perte au feu de 17,4 %.90 g of a yellow precipitate having a loss on ignition of 17.4% are collected.
On détermine un rendement de réaction d'hydrolyse de 82 %.A hydrolysis reaction yield of 82% is determined.
L'analyse par diffraction X permet de déterminer un taux de cristallisation d'environ 65 %.X-ray diffraction analysis makes it possible to determine a crystallization rate of approximately 65%.
On additionne 41,6 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 200 cm³.41.6 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 200 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre (1 M) et un pH voisin de 1.A sol is obtained having a cerium IV concentration expressed in CeO₂ of 172 g / liter (1 M) and a pH close to 1.
L'examen du sol obtenu par diffusion quasi-élastique de la lumière montre la présence de colloïdes ayant un diamètre hydrodynamique moyen de l'ordre de 500 Å et présentant une répartition de taille de colloïdes caractérisée par une variance égale à 0,1.Examination of the soil obtained by quasi-elastic light scattering shows the presence of colloids having an average hydrodynamic diameter of the order of 500 Å and having a size distribution of colloids characterized by a variance equal to 0.1.
On remarque que le sol obtenu présente une bonne stabilité au stockage et ne présente pas de décantation pour une durée d'au moins 6 mois.It is noted that the soil obtained has good storage stability and does not exhibit settling for a period of at least 6 months.
Dans un réacteur muni d'un thermomètre, d'un dispositif d'agitation, d'un système d'introduction de réactifs, d'un réfrigérant ascendant et équipé également d'un dispositif de chauffage, on introduit à température ambiante 1,89 litres d'eau distillée.1.89 is introduced at room temperature into a reactor fitted with a thermometer, a stirring device, a system for introducing reagents, an ascending cooler and also equipped with a heating device. liters of distilled water.
On élève la température de cette solution à 100°C, sous agitation et l'on additionne pendant 3 heures 1,11 litres d'une solution de nitrate cérique contenant 1,25 moles/litre de cérium IV, 0,05 mole/litre de cérium III et ayant une acidité libre de 0,52 N.The temperature of this solution is raised to 100 ° C., with stirring, and 1.11 liters of an ceric nitrate solution containing 1.25 moles / liter of cerium IV, 0.05 moles / liter of cerium III and having a free acidity of 0.52 N.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 80 g/litre et le rapport molaire [H⁺]/[CeIV éq.] est égal à 0,4.In the hydrolysis medium, the concentration of IV cerium expressed as CeO₂ is equal to 80 g / liter and the molar ratio [H⁺] / [Ce IV eq.] Is equal to 0.4.
On maintient le milieu réactionnel sous agitation et au reflux pendant 3 heures.The reaction medium is kept under stirring and at reflux for 3 hours.
On effectue la filtration sur verre fritté. (porosité no 3).Filtration is carried out on sintered glass. (porosity No. 3).
On sèche le produit obtenu dans une étuve à 40°C pendant 48 heures.The product obtained is dried in an oven at 40 ° C for 48 hours.
On recueille 250 g d'un composé répondant à la formule (Ic) et contenant 80 % en poids de CeO₂.250 g of a compound corresponding to formula (Ic) are collected and containing 80% by weight of CeO₂.
On détermine un rendement de réaction d'hydrolyse de 84 %.A hydrolysis reaction yield of 84% is determined.
On additionne 53, 75 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 250 cm³.53.75 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 250 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre (1 M).A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 172 g / liter (1 M).
L'examen par diffusion quasi-élastique de la lumière montre la présence de colloïdes de diamètre hydrodynamique moyen de l'ordre de 450 Å.Examination by quasi-elastic light scattering shows the presence of colloids with an average hydrodynamic diameter of the order of 450 Å.
Dans le dispositif tel que décrit dans l'exemple 6, on introduit à température ambiante, 2,182 litres d'une solution d'acide nitrique 0,518 N.In the device as described in example 6, 2.182 liters of a 0.518 N nitric acid solution are introduced at ambient temperature.
On élève la température de cette solution à 100°C, sous agitation et l'on additionne pendant 3 heures, 817,6 cm³ d'une solution de nitrate cérique contenant 1,28 moles/litre de cérium IV, 0,06 mole/litre de cérium III et ayant une acidité libre de 0,53 N.The temperature of this solution is raised to 100 ° C., with stirring, and 817.6 cm³ of a ceric nitrate solution containing 1.28 moles / liter of IV cerium, 0.06 mole / are added for 3 hours. liter of cerium III and having a free acidity of 0.53 N.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 60 g/litre et le rapport molaire [H⁺]/[CeIV éq.] est égal à 1,5.In the hydrolysis medium, the concentration of IV cerium expressed as CeO₂ is equal to 60 g / liter and the molar ratio [H⁺] / [Ce IV eq.] Is equal to 1.5.
On maintient le milieu réactionnel sous agitation et au reflux pendant 3 heures.The reaction medium is kept under stirring and at reflux for 3 hours.
On effectue la filtration sur verre fritté. (porosité no 3).Filtration is carried out on sintered glass. (porosity No. 3).
On sèche le produit obtenu dans une étuve à 40°C pendant 48 heures.The product obtained is dried in an oven at 40 ° C for 48 hours.
On recueille 180 g d'un composé répondant à la formule (Ic) et contenant 82,6 % en poids de CeO₂.180 g of a compound corresponding to formula (Ic) are collected and containing 82.6% by weight of CeO₂.
On détermine un rendement de réaction d'hydrolyse de 82,5 %.A hydrolysis reaction yield of 82.5% is determined.
On additionne 52 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 250 cm³.52 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 250 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre (1 M).A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 172 g / liter (1 M).
L'examen par diffusion quasi-élastique de la lumière montre la présence de colloïdes de diamètre hydrodynamique moyen de l'ordre de 470 Å.Examination by quasi-elastic light scattering shows the presence of colloids with an average hydrodynamic diameter of the order of 470 Å.
Dans le dispositif tel que décrit dans l'exemple 6, on introduit à température ambiante 2,455 litres d'une solution d'acide nitrique 0,59 N.2.455 liters of a 0.59 N nitric acid solution are introduced into the device as described in Example 6.
On élève la température de cette solution à 100°C , sous agitation et l'on additionne pendant 3 heures, 545 cm³ d'une solution de nitrate cérique contenant 1,28 moles/litre de cérium IV, 0,06 mole/ litre de cérium III et ayant une acidité libre de 0,53 N.The temperature of this solution is raised to 100 ° C., with stirring, and 545 cm³ of a ceric nitrate solution containing 1.28 moles / liter of IV cerium, 0.06 mole / liter of cerium III and having a free acidity of 0.53 N.
Dans le milieu d'hydrolyse. La concentration en cérium IV exprimée en CeO₂ est égale à 40 g/litre et le rapport molaire [H⁺]/[CeIV éq.] est égal à 2,5.In the hydrolysis medium. The concentration of cerium IV expressed in CeO₂ is equal to 40 g / liter and the molar ratio [H⁺] / [Ce IV eq.] Is equal to 2.5.
On maintient le milieu réactionnel sous agitation et au reflux pendant 3 heures.The reaction medium is kept under stirring and at reflux for 3 hours.
On effectue la filtration sur verre fritté. (porosité no 3).Filtration is carried out on sintered glass. (porosity No. 3).
On sèche le produit obtenu dans une étuve à 40°C pendant 48 heures.The product obtained is dried in an oven at 40 ° C for 48 hours.
On recueille 133,6 g d'un composé répondant à la formule (Ic) contenant 83 % en poids de CeO₂.133.6 g of a compound corresponding to formula (Ic) containing 83% by weight of CeO₂ are collected.
On détermine un rendement de réaction d'hydrolyse de 92,5 %.A hydrolysis reaction yield of 92.5% is determined.
On additionne 51,8 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volme de 250 cm³.51.8 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 250 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre (1 M).A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 172 g / liter (1 M).
L'examen par diffusion quasi-élastique de la lumière montre la présence de colloïdes de diamètre hydrodynamique moyen de l'ordre de 570 Å.Examination by quasi-elastic light scattering shows the presence of colloids with an average hydrodynamic diameter of the order of 570 Å.
Dans un réacteur ayant une capacité utile de 900 cm³, équipé d'un dispositif d'agitation, d'un système d'introduction de réactifs, d'un réfrigérant ascendant et d'un dispositif de chauffage régulé à 100°C, d'un système d'écoulement par trop plein, on introduit simultanément et en continu une solution d'eau distillée, à raison de 430 cm³/heure et une solution aqueuse de nitrate cérique contenant 1,23 moles/litre de cérium IV, 0,07 mole/litre de cérium III et ayant une acidité libre de 0,49 N, à raison de 170 cm³/heure.In a reactor with a useful capacity of 900 cc, equipped with a stirring device, a system for introducing reagents, an ascending coolant and a heating device regulated at 100 ° C., an overflow system, a solution of distilled water is introduced simultaneously and continuously, at the rate of 430 cm³ / hour and an aqueous solution of ceric nitrate containing 1.23 moles / liter of cerium IV, 0.07 mole / liter of cerium III and having a free acidity of 0.49 N, at a rate of 170 cm³ / hour.
Un deuxième réacteur similaire au précédent est disposé de manière à recueillir par gravité le mélange réactionnel issu du premier réacteur.A second reactor similar to the previous one is arranged so as to collect by gravity the reaction mixture coming from the first reactor.
Au bout de 9 heures requises pour l'établissement du régime permanent, on réalise pendant 1 heure 30 minutes, un prélèvement en sortie du deuxième réacteur.After 9 hours required for establishing the steady state, a sample is taken for 1 hour 30 minutes at the outlet of the second reactor.
On effectue la filtration sur verre fritté.Filtration is carried out on sintered glass.
On sèche le produit obtenu dans une étuve à 40°C pendant 48 heures.The product obtained is dried in an oven at 40 ° C for 48 hours.
On recueille 60 g d'un précipité jaune contenant 82 % en poids de CeO₂.60 g of a yellow precipitate containing 82% by weight of CeO₂ are collected.
On additionne 52,4 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 250 cm³.52.4 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 250 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre (1 M).A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 172 g / liter (1 M).
L'examen par diffusion quasi-élastique de la lumière montre la présence de colloïdes de diamètre hydrodynamique moyen de l'ordre de 600 Å.Examination by quasi-elastic light scattering shows the presence of colloids with an average hydrodynamic diameter of the order of 600 Å.
Dans l'appareillage tel que décrit dans l'exemple 9, on introduit simultanément et en continu une solution aqueuse d'acide nitrique 0,53 N à raison de 430 cm³/heure et une solution aqueuse de nitrate cérique contenant 1,23 moles/litre de cérium IV, 0,07 mole/litre de cérium III et ayant une acidité libre de 0,49 N, à raison de 170 cm³/heure.In the apparatus as described in Example 9, an aqueous solution of 0.53 N nitric acid is added simultaneously and continuously at a rate of 430 cm³ / hour and an aqueous solution of ceric nitrate containing 1.23 moles / liter of cerium IV, 0.07 mole / liter of cerium III and having a free acidity of 0.49 N, at a rate of 170 cm³ / hour.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 60 g/litre et le rapport molaire [H⁺]/[CeIV éq.] est égal à 1,5.In the hydrolysis medium, the concentration of IV cerium expressed as CeO₂ is equal to 60 g / liter and the molar ratio [H⁺] / [Ce IV eq.] Is equal to 1.5.
Le mélange réactionnel s'écoule par gravité dans un deuxième réacteur.The reaction mixture flows by gravity into a second reactor.
On effectue la filtration sur verre fritté.Filtration is carried out on sintered glass.
On sèche le produit obtenu dans une étuve à 40°C pendant 48 heures.The product obtained is dried in an oven at 40 ° C for 48 hours.
On recueille 52 g d'un précipité jaune contenant 83 % en poids de CeO₂.52 g of a yellow precipitate containing 83% by weight of CeO₂ are collected.
On additionne 51,8 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 250 cm³.51.8 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 250 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre (1 M).A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 172 g / liter (1 M).
L'examen par diffusion quasi-élastique de la lumière montre la présence de colloïdes de diamètre hydrodynamique moyen de l'ordre de 550 Å.Examination by quasi-elastic light scattering shows the presence of colloids with an average hydrodynamic diameter of the order of 550 Å.
Dans cet exemple on utilise à titre de matière première de départ, une solution de nitrate cérique préparée de la manière qui suit :In this example, as starting raw material, a ceric nitrate solution prepared as follows is used:
Dans un réacteur en verre muni d'un dispositif d'agitation, on introduit 1,17 litres d'une solution d'acide nitrique concentré 15 N et 0,61 litre d'eau distillée et l'on chauffe jusqu'à ébullition.1.17 liters of a 15 N concentrated nitric acid solution and 0.61 liters of distilled water are introduced into a glass reactor fitted with a stirring device and the mixture is heated until boiling.
Dans l'acide nitrique chaud, on introduit 670 g d'oxyde cérique hydraté contenant 495 g de CeO₂. Ce dernier est obtenu de façon classique par précipitation à l'ammoniaque et eau oxygénée d'une solution de nitrate céreux (cf FR-A-2 416 867) et n'est pas dispersable dans l'eau.670 g of hydrated ceric oxide containing 495 g of CeO₂ are introduced into hot nitric acid. The latter is obtained conventionally by precipitation with ammonia and hydrogen peroxide from a cerous nitrate solution (cf. FR-A-2 416 867) and is not dispersible in water.
En laissant sous agitation pendant une demie heure à chaud, on obtient 2,02 litres d'une solution de nitrate cérique contenant 1,43 moles/litre de cérium IV, 0,03 mole/litre de cérium III et une acidité libre de 2,9 N.Leaving with stirring for half an hour while hot, 2.02 liters of a ceric nitrate solution containing 1.43 moles / liter of cerium IV, 0.03 moles / liter of cerium III and a free acidity of 2 are obtained. , 9 N.
Dans un réacteur muni d'un thermomètre, d'un dispositif d'agitation, d'un système d'introduction de réactifs, d'un réfrigérant ascendant et équipé d'un dispositif de chauffage, on introduit à température ambiante 2,52 litres d'eau distillée.2.52 liters are introduced into a reactor fitted with a thermometer, a stirring device, a system for introducing reagents, an ascending cooler and equipped with a heating device. distilled water.
On élève la température de cette solution à 100°C sous agitation et on additionne pendant 3 heures 0,485 litre de la solution de nitrate cérique à 1,43 moles/litre de cérium IV préparée précédemment.The temperature of this solution is raised to 100 ° C. with stirring and 0.485 liters of the ceric nitrate solution containing 1.43 moles / liter of IV cerium previously prepared is added for 3 hours.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 40 g/litre et le rapport molaire [H⁺]/[CeIV éq.] est égal à 2.In the hydrolysis medium, the concentration of IV cerium expressed as CeO₂ is equal to 40 g / liter and the molar ratio [H⁺] / [Ce IV eq.] Is equal to 2.
On maintient le milieu réactionnel sous agitation et au reflux pendant 3 heures.The reaction medium is kept under stirring and at reflux for 3 hours.
On effectue la filtration sur verre fritté (porosité no 3) et on sèche le produit obtenu à 40°C pendant 48 heures.Filtration is carried out on sintered glass (porosity No. 3) and the dried product obtained at 40 ° C for 48 hours.
On recueille 130 g d'un précipité jaune.130 g of a yellow precipitate are collected.
L'analyse chimique du produit obtenu montre qu'il présente la composition suivante :
- CeO₂ = 83,9 %
- rapport molaire NO₃⁻/CeIV = 0,35Chemical analysis of the product obtained shows that it has the following composition:
- CeO₂ = 83.9%
- NO₃⁻ / Ce IV molar ratio = 0.35
On détermine un rendement de réaction d'hydrolyse de 92 %.A hydrolysis reaction yield of 92% is determined.
On additionne 51 g d'hydrate ainsi préparé dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 250 cm³51 g of hydrate thus prepared are added in distilled water used in sufficient quantity to obtain a volume of 250 cm³
On obtient un sol ayant une concentration en cérium IV de 1 mole/litre.A soil is obtained having a concentration of IV cerium of 1 mole / liter.
L'examen par diffusion quasi-élastique de la lumière montre la présence de colloïdes de diamètre hydrodynamique moyen de l'ordre de 360 Å.Examination by quasi-elastic light scattering shows the presence of colloids with an average hydrodynamic diameter of the order of 360 Å.
On prépare un composé de cérium IV selon le mode opératoire de l'exemple 4 à l'exception de l'opération de séchage qui est supprimée.A cerium IV compound is prepared according to the procedure of Example 4 with the exception of the drying operation which is omitted.
L'analyse chimique du produit obtenu est la suivante :
- perte au feu = 41,8 %
- CeO₂ = 58,2 %
- rapport molaire NO₃⁻/CeIV = 0,4The chemical analysis of the product obtained is as follows:
- loss on ignition = 41.8%
- CeO₂ = 58.2%
- NO₃⁻ / Ce IV molar ratio = 0.4
On additionne 60,3 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 200 cm³.60.3 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 200 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre (1 M) et un pH d'environ 1,2.A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 172 g / liter (1 M) and a pH of approximately 1.2.
L'examen du sol obtenu par diffusion quasi-élastique de la lumière révèle la présence de colloïdes ayant un diamètre hydrodynamique moyen de l'ordre de 630 Å et une répartition de taille de colloïdes caractérisée par une variance égale à 0,21.Examination of the soil obtained by quasi-elastic light scattering reveals the presence of colloids having an average hydrodynamic diameter of the order of 630 Å and a size distribution of colloids characterized by a variance equal to 0.21.
Dans un ballon tricol de 2 litres muni d'un thermomètre, d'un dispositif d'agitation, d'un système d'introduction de réactifs, d'un réfrigérant ascendant et équipé également d'un dispositif de chauffage, on introduit à température ambiante :
- 1425 cm³ d'eau distillée
- 558 cm³ d'une solution de nitrate cérique contenant 1,24 moles/litre de cérium IV, 0,06 mole/litre de cérium III et ayant une acidité libre de 0,8 N.The temperature is introduced into a 2-liter three-necked flask provided with a thermometer, a stirring device, a system for introducing reagents, an ascending refrigerant and also equipped with a heating device. ambient:
- 1425 cm³ of distilled water
- 558 cm³ of a ceric nitrate solution containing 1.24 moles / liter of cerium IV, 0.06 moles / liter of cerium III and having a free acidity of 0.8 N.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 60 g/litre et le rapport molaire H⁺/CeIV est égal à 0,64.In the hydrolysis medium, the concentration of cerium IV expressed as CeO₂ is equal to 60 g / liter and the molar ratio H⁺ / Ce IV is equal to 0.64.
On maintient le milieu réactionnel sous agitation et au reflux pendant 4 heures.The reaction medium is kept under stirring and at reflux for 4 hours.
On effectue la filtration sur verre fritté (porosité no 3) en couche mince ( < 5 mm) et sous pression réduite (160 mm de mercure) et l'on tasse au maximum le gâteau pour assurer un essorage poussé.Filtration is carried out on sintered glass (porosity No. 3) thin layer (<5 mm) and reduced pressure (160 mm Hg) and the cup is maximally cake to ensure a high spin.
On recueille 157 g d'un précipité jaune.157 g of a yellow precipitate are collected.
L'analyse chimique du produit obtenu montre qu'il présente la composition suivante :
- perte au feu = 17,5 %
- CeO₂ = 72,5 %
- rapport molaire NO₃⁻/CeIV = 0,45Chemical analysis of the product obtained shows that it has the following composition:
- loss on ignition = 17.5%
- CeO₂ = 72.5%
- NO₃⁻ / Ce IV molar ratio = 0.45
On détermine un rendement de réaction d'hydrolyse de 96 %.A hydrolysis reaction yield of 96% is determined.
On additionne 56 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 200 cm³.56 g of the compound prepared according to a) are added to distilled water used in an amount sufficient to obtain a volume of 200 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 200 g/litre (1,16 M) et un pH de 1,2.A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 200 g / liter (1.16 M) and a pH of 1.2.
L'examen du sol par diffusion quasi-élastique de la lumière révèle la présence de colloïdes ayant un diamètre hydrodynamique moyen d'environ 600 Å.Examination of the soil by quasi-elastic light scattering reveals the presence of colloids having an average hydrodynamic diameter of around 600 Å.
On reprend l'exemple 13 à la différence près que l'on introduit en 3 heures, 558 cm³ de ladite solution de nitrate cérique dans 1425 cm³ d'eau dont la température a été au préalable portée à 100°C.Example 13 is repeated, with the difference that 558 cm³ of said ceric nitrate solution in 1425 cm³ of water are introduced over 3 hours, the temperature of which has been previously brought to 100 ° C.
Dans le milieu d'hydrolyse, la concentration en cérium IV exprimée en CeO₂ est égale à 60 g/litre et le rapport molaire H⁺/CeIV est égal à 0,64.In the hydrolysis medium, the concentration of cerium IV expressed as CeO₂ is equal to 60 g / liter and the molar ratio H⁺ / Ce IV is equal to 0.64.
On maintient le milieu réactionnel sous agitation et au reflux pendant 3 heures.The reaction medium is kept under stirring and at reflux for 3 hours.
On effectue la filtration sur verre fritté (porosité no 3) en couche mince (< 5 mm) et sous pression réduite (160 mm de mercure) et l'on tasse au maximum le gâteau pour assurer un essorage poussé.Filtration is carried out on sintered glass (porosity No. 3) thin layer (<5 mm) and reduced pressure (160 mm Hg) and the cup is maximally cake to ensure a high spin.
On sèche le produit obtenu à 20°C pendant 15 h.The product obtained is dried at 20 ° C for 15 h.
On recueille 146 g d'un précipité jaune.146 g of a yellow precipitate are collected.
L'analyse chimique du produit obtenu présente la composition chimique suivante :
- perte au feu = 23,4 %
- CeO₂ = 76,6 %
- rapport molaire NO₃⁻/CeIV = 0,37The chemical analysis of the product obtained has the following chemical composition:
- loss on ignition = 23.4%
- CeO₂ = 76.6%
- NO₃⁻ / Ce IV molar ratio = 0.37
On détermine un rendement d'hydrolyse de 94 %.A hydrolysis yield of 94% is determined.
On additionne 45 g du composé préparé selon a) dans de l'eau distillée mise en oeuvre en quantité suffisante pour obtenir un volume de 200 cm³.45 g of the compound prepared according to a) are added to distilled water used in sufficient quantity to obtain a volume of 200 cm³.
On obtient un sol ayant une concentration en cérium IV exprimée en CeO₂ de 172 g/litre.A sol is obtained having a concentration of cerium IV expressed in CeO₂ of 172 g / liter.
L'examen du sol obtenu par diffusion quasi-élastique de la lumière révèle le présence de colloïdes ayant un diamètre hydrodynamique moyen d'environ 200 Å et un pH de 1,2.Examination of the soil obtained by quasi-elastic light scattering reveals the presence of colloids having an average hydrodynamic diameter of around 200 Å and a pH of 1.2.
L'état d'agrégation des cristallites est élevé et semblable à celui mis en évidence par la figure 2.The state of aggregation of the crystallites is high and similar to that shown in FIG. 2.
On remarque que le sol obtenu présente une bonne stabilité au stockage et ne présente pas de décantation pour une durée d'au moins 6 mois.It is noted that the soil obtained has good storage stability and does not exhibit settling for a period of at least 6 months.
Claims (41)
Ce(OH)x(NO₃)y, pCeO₂, nH₂O (I)
dans laquelle :
- x est tel que x = 4 - y
- y est compris entre 0,35 et 1,5
- p est supérieur ou égal à 0 et inférieur ou égal à 2,0
- n est supérieur ou égal à 0 et inférieur ou égal à environ 201 - Compound of cerium IV directly dispersible in water corresponding to the general formula (I):
Ce (OH) x (NO₃) y , pCeO₂, nH₂O (I)
in which :
- x is such that x = 4 - y
- is between 0.35 and 1.5
- p is greater than or equal to 0 and less than or equal to 2.0
- n is greater than or equal to 0 and less than or equal to about 20
Ce(OH)x(NO₃)y, nH₂O (Ia)
dans laquelle :
- x est tel que x = 4 - y
- y est compris entre 0,35 et 0,7
- p est supérieur ou égal à 0 et inférieur ou égal à environ 202- Compound of cerium IV according to claim 1 characterized in that it corresponds to formula (Ia):
Ce (OH) x (NO₃) y , nH₂O (Ia)
in which :
- x is such that x = 4 - y
- is between 0.35 and 0.7
- p is greater than or equal to 0 and less than or equal to approximately 20
Ce(OH)x(NO₃)y (Ib)
dans laquelle :
- x est tel que x = 4 - y
- y est compris entre 0,35 et 0,7
- la teneur en cérium exprimée en % de CeO₂ est comprise entre 77 et 72 %.3- Compound of cerium IV according to claim 1 characterized in that it corresponds to formula (Ib):
Ce (OH) x (NO₃) y (Ib)
in which :
- x is such that x = 4 - y
- is between 0.35 and 0.7
- the cerium content expressed in% of CeO₂ is between 77 and 72%.
Ce(OHx(NO₃)y,pCeO₂ (Ic)
dans laquelle :
- x est tel que x = 4 - y
- y est compris entre 0,35 et 1,5
- p est supérieur à 0 et inférieur ou égal à 2,0
- la teneur en cérium exprimée en % de CeO₂ est supérieure à une valeur comprise entre 77 et 72 % selon que y varie de 0,35 à 0,7.4- Compound of cerium IV according to claim 1 characterized in that it corresponds to formula (Ic):
Ce (OH x (NO₃) y , pCeO₂ (Ic)
in which :
- x is such that x = 4 - y
- is between 0.35 and 1.5
- p is greater than 0 and less than or equal to 2.0
- the cerium content expressed in% of CeO₂ is greater than a value between 77 and 72% depending on whether y varies from 0.35 to 0.7.
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41- aqueous sol according to claim 40 obtained by suspending in water, a cerium IV compound obtained according to a process which consists in a first step to mix with stirring, the solution of cerium IV salt and the medium hydrolysis, then bring the mixture to the reaction temperature, the molar ratio [H⁺] / [Ce IV eq.] is greater than or equal to 0 and less than or equal to 0.75 when the equivalent final concentration of cerium IV is greater than or equal to 0.4 mol / liter or the molar ratio [H⁺] / [This IV eq.] is greater than 0.75 and less than or equal to 3 which .....
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Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT87400600T ATE79838T1 (en) | 1986-03-26 | 1987-03-18 | COMPOUNDS OF CER-IV AND METHODS OF PRODUCTION. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8604346A FR2596380B1 (en) | 1986-03-26 | 1986-03-26 | NOVEL CERIUM IV COMPOUND AND PREPARATION METHOD THEREOF |
| FR8604346 | 1986-03-26 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0239477A2 true EP0239477A2 (en) | 1987-09-30 |
| EP0239477A3 EP0239477A3 (en) | 1987-11-25 |
| EP0239477B1 EP0239477B1 (en) | 1992-08-26 |
Family
ID=9333570
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP87400600A Expired - Lifetime EP0239477B1 (en) | 1986-03-26 | 1987-03-18 | Cerium iv compound and process for its preparation |
Country Status (12)
| Country | Link |
|---|---|
| US (1) | US5035834A (en) |
| EP (1) | EP0239477B1 (en) |
| JP (2) | JP2681464B2 (en) |
| KR (1) | KR910009578B1 (en) |
| AT (1) | ATE79838T1 (en) |
| AU (1) | AU598525B2 (en) |
| BR (1) | BR8701981A (en) |
| CA (1) | CA1332779C (en) |
| DE (1) | DE3781297T2 (en) |
| ES (1) | ES2051760T3 (en) |
| FR (1) | FR2596380B1 (en) |
| GR (1) | GR3006266T3 (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2617153A1 (en) * | 1987-06-26 | 1988-12-30 | Rhone Poulenc Chimie | PROCESS FOR OBTAINING CERIC OXIDE AND CERIC OXIDE WITH NEW MORPHOLOGICAL CHARACTERISTICS |
| EP0300853A1 (en) * | 1987-06-29 | 1989-01-25 | Rhone-Poulenc Chimie | Process for obtaining a cerium oxide |
| FR2621576A1 (en) * | 1987-10-09 | 1989-04-14 | Rhone Poulenc Chimie | COLLOIDAL DISPERSION OF AQUEOUS CERIUM IV COMPOUND AND PROCESS FOR PREPARING THE SAME |
| FR2632945A1 (en) * | 1988-06-15 | 1989-12-22 | Rhone Poulenc Chimie | Process for producing a ceric oxide having a high specific surface |
| FR2831177A1 (en) | 2001-10-22 | 2003-04-25 | Rhodia Elect & Catalysis | Colloidal dispersion of particles of a cerium compound, especially useful in woodstains, comprises a dye covalently bound to the particles through a coupling agent |
| FR2884245A1 (en) * | 2005-04-12 | 2006-10-13 | Inst Nat Sciences Appliq | CERIUM (III) HEXANUCLEAR COMPLEXES AND PROCESS FOR PRODUCING SUCH COMPLEXES. |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2583737B1 (en) * | 1985-06-20 | 1987-08-14 | Rhone Poulenc Spec Chim | NOVEL CERIUM IV COMPOUND AND PREPARATION METHOD THEREOF. |
| US5308548A (en) * | 1985-06-20 | 1994-05-03 | Rhone-Poulenc Specialities Chimiques | Preparing a dispersible, sol-forming cerium (IV) composition |
| FR2608583B1 (en) * | 1986-12-19 | 1990-12-07 | Rhone Poulenc Chimie | CERIC OXIDE WITH NEW MORPHOLOGICAL CHARACTERISTICS AND PROCESS FOR OBTAINING SAME |
| JPH062582B2 (en) * | 1987-12-02 | 1994-01-12 | 多木化学株式会社 | Crystalline ceric oxide sol and method for producing the same |
| JP2746861B2 (en) * | 1995-11-20 | 1998-05-06 | 三井金属鉱業株式会社 | Method for producing ultrafine cerium oxide particles |
| FR2840313B1 (en) | 2002-05-28 | 2004-08-27 | Rhodia Elect & Catalysis | COMPOSITION BASED ON AN AQUEOUS PAINT, IN PARTICULAR A LASURE OR A VARNISH, AND AN AQUEOUS COLLOIDAL DISPERSION OF CERIUM |
| US7229600B2 (en) * | 2003-01-31 | 2007-06-12 | Nanoproducts Corporation | Nanoparticles of rare earth oxides |
| JP4731220B2 (en) * | 2005-06-01 | 2011-07-20 | 第一稀元素化学工業株式会社 | Method for producing ceria sol |
| EP2669045B1 (en) | 2011-01-25 | 2019-09-04 | Konica Minolta, Inc. | Fine abrasive particles and process for producing same |
| FR3043568B1 (en) | 2015-11-13 | 2021-01-29 | Ifp Energies Now | FLUID FOR DEPOLLUTION OF THERMAL ENGINES USING STABLE SUSPENSIONS OF METAL COLLOIDAL PARTICLES AND METHODS OF PREPARATION OF SUCH FLUID |
| CN109534383B (en) * | 2019-01-18 | 2022-10-11 | 江西师范大学 | Synthesis method of cerium dioxide nanosheet |
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| EP0153227A1 (en) * | 1984-02-20 | 1985-08-28 | Rhone-Poulenc Chimie | Cerium dioxide with morphological characteristics, and process for its preparation |
| EP0207857A2 (en) * | 1985-07-03 | 1987-01-07 | Rhone-Poulenc Chimie | Composition containing ceric oxide, its preparation and its use |
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- 1987-03-18 DE DE8787400600T patent/DE3781297T2/en not_active Expired - Fee Related
- 1987-03-18 ES ES87400600T patent/ES2051760T3/en not_active Expired - Lifetime
- 1987-03-18 AT AT87400600T patent/ATE79838T1/en not_active IP Right Cessation
- 1987-03-25 AU AU70605/87A patent/AU598525B2/en not_active Ceased
- 1987-03-25 JP JP62069281A patent/JP2681464B2/en not_active Expired - Fee Related
- 1987-03-25 CA CA000532913A patent/CA1332779C/en not_active Expired - Fee Related
- 1987-03-26 BR BR8701981A patent/BR8701981A/en unknown
- 1987-03-26 US US07/030,134 patent/US5035834A/en not_active Expired - Fee Related
- 1987-03-26 KR KR1019870002808A patent/KR910009578B1/en not_active IP Right Cessation
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| US2327992A (en) * | 1938-04-13 | 1943-08-31 | Blumenfeld Joseph | Process for the preparation of compounds of cerium |
| FR1442597A (en) * | 1965-05-20 | 1966-06-17 | Piesteritz Stickstoff | Process for separating cerium from other rare earths |
| WO1979000248A1 (en) * | 1977-11-01 | 1979-05-17 | Atomic Energy Authority Uk | Production of dispersions |
| GB2075478A (en) * | 1980-05-09 | 1981-11-18 | Atomic Energy Authority Uk | Improvements in or Relating to Cerium Compounds |
| EP0153227A1 (en) * | 1984-02-20 | 1985-08-28 | Rhone-Poulenc Chimie | Cerium dioxide with morphological characteristics, and process for its preparation |
| EP0207857A2 (en) * | 1985-07-03 | 1987-01-07 | Rhone-Poulenc Chimie | Composition containing ceric oxide, its preparation and its use |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2617153A1 (en) * | 1987-06-26 | 1988-12-30 | Rhone Poulenc Chimie | PROCESS FOR OBTAINING CERIC OXIDE AND CERIC OXIDE WITH NEW MORPHOLOGICAL CHARACTERISTICS |
| EP0298808A1 (en) * | 1987-06-26 | 1989-01-11 | Rhone-Poulenc Chimie | Process for obtaining cerium (IV) oxide and cerium (IV) oxide with novel morphological characteristics |
| US4965057A (en) * | 1987-06-26 | 1990-10-23 | Rhone-Poulenc Chimie | Process for producing morphologically improved ceric oxide particulates |
| AU610898B2 (en) * | 1987-06-26 | 1991-05-30 | Rhone-Poulenc Chimie | Procedure for the production of a ceric oxide and ceric oxide with novel morphological characteristics |
| EP0300853A1 (en) * | 1987-06-29 | 1989-01-25 | Rhone-Poulenc Chimie | Process for obtaining a cerium oxide |
| FR2621576A1 (en) * | 1987-10-09 | 1989-04-14 | Rhone Poulenc Chimie | COLLOIDAL DISPERSION OF AQUEOUS CERIUM IV COMPOUND AND PROCESS FOR PREPARING THE SAME |
| EP0316205A1 (en) * | 1987-10-09 | 1989-05-17 | Rhone-Poulenc Chimie | Colloidal dispersion of a cerium IV compound in an aqueous medium, and process for its preparation |
| FR2632945A1 (en) * | 1988-06-15 | 1989-12-22 | Rhone Poulenc Chimie | Process for producing a ceric oxide having a high specific surface |
| FR2831177A1 (en) | 2001-10-22 | 2003-04-25 | Rhodia Elect & Catalysis | Colloidal dispersion of particles of a cerium compound, especially useful in woodstains, comprises a dye covalently bound to the particles through a coupling agent |
| FR2884245A1 (en) * | 2005-04-12 | 2006-10-13 | Inst Nat Sciences Appliq | CERIUM (III) HEXANUCLEAR COMPLEXES AND PROCESS FOR PRODUCING SUCH COMPLEXES. |
| WO2006108798A2 (en) * | 2005-04-12 | 2006-10-19 | Institut National Des Sciences Appliquees De Rennes | Hexanuclear cerium (iii) complexes and method for making same |
| WO2006108798A3 (en) * | 2005-04-12 | 2007-03-08 | Inst Nat Sciences Appliq | Hexanuclear cerium (iii) complexes and method for making same |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2596380B1 (en) | 1991-09-27 |
| CA1332779C (en) | 1994-11-01 |
| US5035834A (en) | 1991-07-30 |
| GR3006266T3 (en) | 1993-06-21 |
| ES2051760T3 (en) | 1994-07-01 |
| JPH0748123A (en) | 1995-02-21 |
| AU7060587A (en) | 1987-10-01 |
| AU598525B2 (en) | 1990-06-28 |
| BR8701981A (en) | 1988-01-12 |
| JPH0811690B2 (en) | 1996-02-07 |
| KR870008790A (en) | 1987-10-20 |
| KR910009578B1 (en) | 1991-11-21 |
| FR2596380A1 (en) | 1987-10-02 |
| JPS62275021A (en) | 1987-11-30 |
| DE3781297D1 (en) | 1992-10-01 |
| EP0239477A3 (en) | 1987-11-25 |
| EP0239477B1 (en) | 1992-08-26 |
| JP2681464B2 (en) | 1997-11-26 |
| ATE79838T1 (en) | 1992-09-15 |
| DE3781297T2 (en) | 1993-03-18 |
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